GMC Frame Mounts

[BigDan3131]

So after going through a bunch of pages most if not all the swap info is for the Chevy. My Jimmy [1965] had the 305E with powerglide and I want to reuse the stock frame mounts if I can. They are mounted in the forward holes and I want max set back for better handling. It will be a 6.0L/TH350 with long tube headers.
Has anyone made a motor plate instead of using side mounts? As far as solid mounts go I think the "rattle your teeth loose" is a myth. If you had low profile tires and a rigid suspension with race seats then yes you would feel it. Comfy seats with tires having a larger profile and a softer suspension you wont feel it.
Just like aluminum door panels "rattle" that's BS too.

[BR3W CITY]

The filled mounts or poly mounts aren't bad, but a motor plate WILL provide more rattle and shake. I've never been in a sub 400hp car with a motor plate, but anything I've been in with one has been VERY harsh, given many of these were 1k+ hp, so everything about them is harsh regardless.

Have you looked at whats availabe, or do you want to fab one? And are you interested in a front motor plate or a mid-plate? I saw this for $75 and it was tempting.

http://compare.ebay.com/like/1110495...Types&var=sbar

[BigDan3131]

Do you need both a front and a mid plate if I were to go that route?

[BR3W CITY]

I've gotten mixed feelings on this, but my answer is no. You can run solid mounts, a front plate and possibly a limiter of sorts and be fine. Mid plates are kind of a beast to work around. I see mid plates more commonly used on higher hp cars, some of which require a unique mounting position (or height), like a car with a punched firewall and the engine setback....they also allow you to run longtubes.

With something long like a bbc and a 'glide, you can put stress on the bellhousing without a midplate, because the only support to the combo would be the front plate and the rear of the trans mount. (assuming that the side mounts had been removed in favor of the mid plate)

[crazy longhorn]

I am not nuts about a solid mount , on a street vehicle. Any vibe you will get, will be mostly "tin rattle" @ idle, & I have some of that with the poly mounts in my truck. If the chassis is not fairly ridged, & racetrack bound....I don't see the need for a solid mount, or engine plates. just my thoughts? crazyL

[BigDan3131]

After reading other forums about the subject it seems the real race only guys like to use both a front plate and regular side mounts for I guess extra rigidness. So since the 6.0L block is iron I'm going to build my own that combines the two, side and front together. It will be made of steel since I'm sure aluminum would weld itself to the iron block over time.
I remember a racer once told me if I use a poly trans mount with the solid motor mounts it would be enough give in the system to last and it has. Its what I have on my El Camino which makes only about 486 HP at the crank and has been trouble free since 1996.
Getting back to the mount I will make it adjustable enough to go two inches either way and mounting it will be just 4 pieces of plate gusseted for strength with 2 half inch bolts.