67-72 frame conversion for 63 Knee Knocker Cab and Bed

[66-PMD-GMC]

I recently purchased a 69 SWB frame that is setup for power steering, it has the factory "notch" for the power steering gear box.
My plan is to use it under my 63 truck cab and bed.
Unlike any of my GMC's this frame has trailing arms instead of the leaf springs on the rear. Good for what I am looking to do with the truck
My question is, has anyone in this forum done a conversion of this type, the 67-72 frame for a 60-66 cab and kept a photo log of it start to finish?
I see the rear cab mounts and first few inches of the frame horns are different. Also a cross member that is rivited on at the front is also different.
I have a 5 lug/disk front suspension and I am wondering if there are any 5 lug rear diff's that will bolt in or is buying two new 5 lug axles the way to go?
I have a new digital camera in hand and I will be starting by tacking new frame horns on the front of the frame and go from there.
Just so anyone reading this knows, I have done the adapter bit for power steering and other adapted mods and while the end result was functional, it wasn't what I call pretty or did it look factory.
My aim is to build a clean looking 4 wheeled rocket and have every aspect look factory original whether it was or not.

[SCOTI]

Originally Posted by 66-PMD-GMC

I recently purchased a 69 SWB frame that is setup for power steering, it has the factory "notch" for the power steering gear box.
My plan is to use it under my 63 truck cab and bed.
Unlike any of my GMC's this frame has trailing arms instead of the leaf springs on the rear. Good for what I am looking to do with the truck
My question is, has anyone in this forum done a conversion of this type, the 67-72 frame for a 60-66 cab and kept a photo log of it start to finish?
I see the rear cab mounts and first few inches of the frame horns are different. Also a cross member that is rivited on at the front is also different.
I have a 5 lug/disk front suspension and I am wondering if there are any 5 lug rear diff's that will bolt in or is buying two new 5 lug axles the way to go?
I have a new digital camera in hand and I will be starting by tacking new frame horns on the front of the frame and go from there.
Just so anyone reading this knows, I have done the adapter bit for power steering and other adapted mods and while the end result was functional, it wasn't what I call pretty or did it look factory.
My aim is to build a clean looking 4 wheeled rocket and have every aspect look factory original whether it was or not.

My 'Recycle' build is based on a 68lwb frame but I don't have specific pics per say of the 'differences':

Front frame horns different height & physical shape
Radiator core support mounts (fore/aft location vs front x-member C/L)
Radiator core support mount height (63-66 core support vs. 67-72)
Front splash apron (specific to post 66 trucks?)
Rear cab mount height

I have seen a pre 67 body on a post 66 frame w/o doing any mods other than cutting the frame horns off (they installed a crude roll-pan). While it physically swapped, you could tell things were not square & were binding @ the mounts. I preferred an OE/professional look for my swap & opted to relocated & change things as necessary.

For the 5-lug swap, I would get replacement axles in for the 5-lug pattern if you know your current rear end is decent. The axle swap is fairly easy (especially vs swapping another housing into place) & you'll have 100% new, zero bearing wear, stronger than OE axles vs. 30yr old axles. Then just get some 71-72 drums from your local parts store.

[66-PMD-GMC]

Originally Posted by SCOTI

My 'Recycle' build is based on a 68lwb frame but I don't have specific pics per say of the 'differences':

Front frame horns different height & physical shape
Radiator core support mounts (fore/aft location vs front x-member C/L)
Radiator core support mount height (63-66 core support vs. 67-72)
Front splash apron (specific to post 66 trucks?)
Rear cab mount height

I have seen a pre 67 body on a post 66 frame w/o doing any mods other than cutting the frame horns off (they installed a crude roll-pan). While it physically swapped, you could tell things were not square & were binding @ the mounts. I preferred an OE/professional look for my swap & opted to relocated & change things as necessary.

For the 5-lug swap, I would get replacement axles in for the 5-lug pattern if you know your current rear end is decent. The axle swap is fairly easy (especially vs swapping another housing into place) & you'll have 100% new, zero bearing wear, stronger than OE axles vs. 30yr old axles. Then just get some 71-72 drums from your local parts store.

I have the 2 frames side by side and see the differences along with the similarities.
I am using an old LWB frame for all of the donor parts (cross members, supports etc.) and as a template for hole placement etc. etc..
I think it will be worth the trouble in the end.
I will also be boxing a good portion of the frame as the torque from the motor I am using will be a factor. I don't want a roll cage if I can avoid it.
Your link to your build didn't work. I'll look for it.

[66-PMD-GMC]

SCOTI, found your build. I have actually followed your thread for a while.


I was looking at the frames tonight before a little dust storm blew through and it sure looks as if the bottom half of the frame horn is the same between the 63-66 frame and the 67-72 frame. I am going to make a template to check for sure.
The rad. support is different but that looks pretty easy to swap out.
Suspension in front is the same and bed perches look the same.
Front cab mounts look the same and the rear mounts are definitely in need of swapping.

The grinder will come out soon and brackets are coming off.
I am going to need a box of grade 8 X 1/2" bolts and nuts to reassemble.
I am leaning toward the 3 step brush on frame coating.

[SCOTI]

Originally Posted by 66-PMD-GMC

SCOTI, found your build. I have actually followed your thread for a while.


I was looking at the frames tonight before a little dust storm blew through and it sure looks as if the bottom half of the frame horn is the same between the 63-66 frame and the 67-72 frame. I am going to make a template to check for sure.
The rad. support is different but that looks pretty easy to swap out.
Suspension in front is the same and bed perches look the same.
Front cab mounts look the same and the rear mounts are definitely in need of swapping.

The grinder will come out soon and brackets are coming off.
I am going to need a box of grade 8 X 1/2" bolts and nuts to reassemble.
I am leaning toward the 3 step brush on frame coating.

The transition on the front rails to the frame horns was slightly different as well. Enough so that when I did mine, I used frame horns off of the 'correct' year frame as my bumper brackets (similar to how a rear bumper/late model front bumper attaches). My 'new' brackets have a short extension of the top side of the frame rail still on them so that when installed, the gap between the front sheetmetal above the rails looks 'correct'.

You might consider adding spacers for the rear cab mounts & getting longer rear bolts. I built new ones (from the old ones) only because I added gusset/fish plates to my rails which changed the width dimensions. Since the mounts were going to be off, I just re-did them w/the right dimensions. A stock width frame could utilize some 1" spacers under the cab bushings & would be good to go. Rattle can them black & use a poker face. I won't tell

[jmcdaniel]

I am very interested in this thread. i am using a 70 swb frame for a 63 cab and front end as well. if i am understanding correctly, i won't be able to mount the front bumper correctly w/o mods, and my radiator won't mount either using the 70 frame. i have the 70 radiator with me but i am still unsure if i will need to relocate. also, are the cab holes in the right locations and its just that the rear cab mounts on the 70 frame are an 1" shorter so i can either add/make a spacer or just grind the rear mounts off and make new ones. help a brotha out. thx.

[SCOTI]

i am using a 70 swb frame for a 63 cab and front end as well. if i am understanding correctly, i won't be able to mount the front bumper correctly w/o mods,

Correct. They are physically a different shape which prevents the bumper from seating completely & @ the correct angle. There will be some fabrication required.

my radiator won't mount either using the 70 frame? i have the 70 radiator with me but i am still unsure if i will need to relocate.

The pre-67's radiator mount is separate from the core support. On the 70 frame, it's part of the core support. The 70 radiator could prob be used, but would require cutting some of your 63's inner fender wells for clearance. I'm going to just build a 'new' radiator mount (similar to what worked on the pre-67 frame) that fits in front of the core support once the sheetmetal is swapped or make it part of my 64's core support (like the post-67 setup). I will use the correct style radiator for my 64.

are the cab holes in the right locations and its just that the rear cab mounts on the 70 frame are an 1" shorter so i can either add/make a spacer or just grind the rear mounts off and make new ones.

Correct. If I remember correctly, the pre-67 rear cab mounts were 1-1.125" higher vs. the post 67 cab mounts. A solid 1" spacer should work & then use shims as req'd to dial-in the cab/bed alignment.

One thing you didn't mention is the radiator core support mounts. My measuring indicated they were @ a slightly different height as well as fore/aft location. They also required some tweaking. You could mount the cab & then just relocate the mounts as req'd. I remember it didn't take much, but wouldn't work 'as-is' either.

The truck that I saw w/this conversion (@ a frame straigtening joint) didn't move the mounts & it was obvious there was something not right. The frame guy was trying to correct the body/chassis alignment issues & I pointed out to him I was starting a similar swap & what the differences were. Whoever did that swap, just wanted the body on there w/o regard to installation quality (round pegs can/do fit in square holes).

[66-PMD-GMC]

Originally Posted by SCOTI

You might consider adding spacers for the rear cab mounts & getting longer rear bolts. I built new ones (from the old ones) only because I added gusset/fish plates to my rails which changed the width dimensions. Since the mounts were going to be off, I just re-did them w/the right dimensions. A stock width frame could utilize some 1" spacers under the cab bushings & would be good to go. Rattle can them black & use a poker face. I won't tell

I measured the frame width on both frames and they are identical within a 1/16 of and inch. The datum holes are also in the same place, dead on, on both frames. (holes used for taking measurements during build and repair of vehicles)
Using these holes as the guide, I find that only the rear cab mounts and front cross members/supports under the radiator are in question.
Are you saying you are finding the front cab mounts in a different location between the 2 year groups? (63-66 and 67-72)
Also, I find that the GMC and Chevy radiator supports are different throughout 60-66 making this quite a mixed bag. So this all will depend on what my desired end result is. Yes?
Theoretically I should be able to strip the brackets and bracing from the 66 frame and use it all on the 69 frame and other than the frame horns, it would be a bolt together deal.
I am generating a blue print as I go since I have been unable to find any prints on the 63-66 GMC frames, only Chevy.
I do have 67-69 prints for what they are but my rudimentary initial measurements tell me there is more similar than dissimilar between the year groups of frames here.

[SCOTI]

Originally Posted by 66-PMD-GMC

Using these holes as the guide, I find that only the rear cab mounts and front cross members/supports under the radiator are in question.
Are you saying you are finding the front cab mounts in a different location between the 2 year groups? (63-66 and 67-72)

The rear cab mounts & front core support mounts are different. Front cab mounts are ok to re-use.

Also, I find that the GMC and Chevy radiator supports are different throughout 60-66 making this quite a mixed bag. So this all will depend on what my desired end result is. Yes?

Yes. This is why I'm waiting to do my radiator mount until after the body is swapped.

[66-PMD-GMC]

Originally Posted by SCOTI

The rear cab mounts & front core support mounts are different. Front cab mounts are ok to re-use.

Yes. This is why I'm waiting to do my radiator mount until after the body is swapped.

OH! OK, I was worried you had found the front cab mounts were in need of changing.
Using the datum holes and sections of the frame as a template, I am certain the radiator support from my donor frame will work just fine since it matches the GMC parts I am using.
I will be taking photos tomorrow and onward.

[jmcdaniel]

in talking about the frame horns and the differences between the models, will i be okay with buying or finding frame horns frome the 60-66 models. if this is a bolt on fix then let me know. if the bolt holes on the frame itself are in a different location where the frame horns connect, then pics would great as well as the radiator issues. thx.

[SCOTI]

Originally Posted by jmcdaniel

in talking about the frame horns and the differences between the models, will i be okay with buying or finding frame horns frome the 60-66 models. if this is a bolt on fix then let me know. if the bolt holes on the frame itself are in a different location where the frame horns connect, then pics would great as well as the radiator issues. thx.

Using the 60-66 horns as bumper 'brackets' to attach to the post-66 frame would work.

The alternative is just splicing (welding) the 60-66 horn ends to the post-66 frame rails. I didn't want to permanently attach them until I could 100% verify they were in the correct position w/the body swapped.

[66-PMD-GMC]

Originally Posted by jmcdaniel

in talking about the frame horns and the differences between the models, will i be okay with buying or finding frame horns frome the 60-66 models. if this is a bolt on fix then let me know. if the bolt holes on the frame itself are in a different location where the frame horns connect, then pics would great as well as the radiator issues. thx.

I will have photos of the frame horn graft today and post them soon after.
I am starting my conversion this morning.

[66-PMD-GMC]

I made a huge typo in a previous post.
I have a number of prints for 63-66 but nothing for 67-72.
This print is one of some that I have and while it isn't perfect, it provides invaluable information. I just wish it were a little clearer.

[66-PMD-GMC]

Initial findings are as follows;
Wheel centerline datum holes, marked by red arrows, on both the 69 and the 63 frame are in identical positions on both frames.
Core support brackets 1.286, marked with black arrows are in the same position on both frames.
Core support/ cross member, marked by yellow arrow is not the same on both frames but frame rails are the same distance and swapping in the correct rail from the donor frame is a simple matter of using clamps, measuring and drilling holes.
Rear cab mounts are as SCOTI mentioned, not close at all between the frames, marked in green arrows. Again, clamped in at the correct height and position they seem relatively easy to install.
I did not get a chance to cut off the correct frame horns and mock them up to measure but I will soon.

[SCOTI]

Originally Posted by 66-PMD-GMC

Initial findings are as follows;
Wheel centerline datum holes, marked by red arrows, on both the 69 and the 63 frame are in identical positions on both frames.
Core support brackets 1.286, marked with black arrows are in the same position on both frames.
Core support/ cross member, marked by yellow arrow is not the same on both frames but frame rails are the same distance and swapping in the correct rail from the donor frame is a simple matter of using clamps, measuring and drilling holes.
Rear cab mounts are as SCOTI mentioned, not close at all between the frames, marked in green arrows. Again, clamped in at the correct height and position they seem relatively easy to install.
I did not get a chance to cut off the correct frame horns and mock them up to measure but I will soon.

Hhmm..... When I measured the core support mount (brkt 1.286), they were @ different heights vs the top of the frame rail when measured from the wheel centerline datum holes as well as a different distance (again measured from the wheel centerline datum holes). It wasn't off by much, but it was different.

If your data is correct, I'm glad I made them a bolt-on.

[66-PMD-GMC]

Originally Posted by SCOTI

Hhmm..... When I measured the core support mount (brkt 1.286), they were @ different heights vs the top of the frame rail when measured from the wheel centerline datum holes as well as a different distance (again measured from the wheel centerline datum holes). It wasn't off by much, but it was different.

If your data is correct, I'm glad I made them a bolt-on.

I haven't finished my frame jig but by eye they looked to be the same height. Once on the jig and with a datum point to measure height I will know for sure.
The measurements have been taken with a tape measure and everything so far has been within 1/16th" or .0625"
All preliminary..... but again, I am just starting.

[chad64chevy]

hey guys, i can say that i too am in the middle of doin the same thing! i have a '64 on a '70 frame, i measured and measured and what i found out was really all it takes is cut the frame horns off, switch the front crossmembers, and switch the rear cab mounts out! if i remember right the rad. core support bracket moved foward like an inch. don't quote me on that i don't have the frame infront of me! i think on mine the rear cab mounts only one hole lined up and i had to drill the other three per side! i'm tryin to remember since i started my conversion last summer! i also am waiting to see if the frame horns are lined up before welding them in! in my build thread you can kind of see that i have a 1/4" plate that my frame horns will be bolted to for now then welded later!

[66-PMD-GMC]

Originally Posted by chad64chevy

hey guys, i can say that i too am in the middle of doin the same thing! i have a '64 on a '70 frame, i measured and measured and what i found out was really all it takes is cut the frame horns off, switch the front crossmembers, and switch the rear cab mounts out! if i remember right the rad. core support bracket moved foward like an inch. don't quote me on that i don't have the frame infront of me! i think on mine the rear cab mounts only one hole lined up and i had to drill the other three per side! i'm tryin to remember since i started my conversion last summer! i also am waiting to see if the frame horns are lined up before welding them in! in my build thread you can kind of see that i have a 1/4" plate that my frame horns will be bolted to for now then welded later!

I am making a template from 1/16th" thick steel plate.
I am convinced the 69 frame I have has a slightly different frame horn angle than the 63 frame.
I am going to form the plate against the 63 frame once the brackets and rivets are all gone and make a drilled profile template that I will pin to the new frame to properly locate the template.
Once done, I will be able to immediately see the differences in the frames from the wheel centerline to the horns and also be able to transfer the holes needed to install the front cross member for the radiator support.
I am going to probably need to remove the radiator support brackets on the 69 frame to use the template but that will tell me where everything should be and also help to line up the frame horns that hold the bumper.
The jig I am making will hold the frame in a parrallel position to gaurentee heights and I will

[jmcdaniel]

I am wondering if there is a place to buy new rear cab mounts as well as the front core support crossmember for the 60-66 trucks. I am still not sure what is called the frame horns. could someone please point them out to me either in the pic that 66-pmd provided or send a pic that shows me. i am thinking that the frame horns are the bumper brackets but i guess i'm wrong. need help plz.

[66-PMD-GMC]

Originally Posted by chad64chevy

hey guys, i can say that i too am in the middle of doin the same thing! i have a '64 on a '70 frame, i measured and measured and what i found out was really all it takes is cut the frame horns off, switch the front crossmembers, and switch the rear cab mounts out! if i remember right the rad. core support bracket moved foward like an inch. don't quote me on that i don't have the frame infront of me! i think on mine the rear cab mounts only one hole lined up and i had to drill the other three per side! i'm tryin to remember since i started my conversion last summer! i also am waiting to see if the frame horns are lined up before welding them in! in my build thread you can kind of see that i have a 1/4" plate that my frame horns will be bolted to for now then welded later!

I am making a template from 1/16th" thick steel plate for the prifile of the front of the frame. (side)
I am convinced the 69 frame I have has a slightly different frame horn angle than the 63 frame. That would explain the differances in height of the bracket to frame top.
I am going to form the plate against the 63 frame once the brackets and rivets are all gone and make a drilled profile template that I will pin to the new frame to properly locate the template.
Once done, I will be able to immediately see the differences in the frames from the wheel centerline to the horns and also be able to transfer the holes needed to install the front cross member for the radiator support.
I am going to probably need to remove the core support brackets on the 69 frame to use the template but that will tell me where everything should be and also help to line up the frame horns that hold the bumper.
The jig I am making will hold the frame in a parallel position to guarantee heights and I will use this to set the rear cab bracket heights.
The rivets by the way, are much tougher little turds than I thought they were going to be.

[66-PMD-GMC]

Originally Posted by jmcdaniel

I am wondering if there is a place to buy new rear cab mounts as well as the front core support crossmember for the 60-66 trucks. I am still not sure what is called the frame horns. could someone please point them out to me either in the pic that 66-pmd provided or send a pic that shows me. i am thinking that the frame horns are the bumper brackets but i guess i'm wrong. need help plz.

Your front bumper mounts to the frame horns directly with 4 bolts.
Hope that helps.

[66-PMD-GMC]

I have seen 67-72 frame mount brackets online but nothing for 63-66 yet.

[SCOTI]

Originally Posted by 66-PMD-GMC

Your front bumper mounts to the frame horns directly with 4 bolts.
Hope that helps.

Don't forget the 2 'outer' brackets that brace the ends. Where it attaches @ the front of the main frame rails are the "frame horns".

[jmcdaniel]

thx scoti, that answers my question about the frame horns. i have one of the outer brackets from the 63 bumper which i hope will help in possible positioning. also, do you think it would be just as easy to make a core support cross member. i don't remember what the 60-66 crossmembers looked like. if it is a straight piece of steel i think it might be cheaper and just as effective to build one. your opinion?