LS1 '48 3100 swap, rpm range, few other questions

[Dustint]

Swapping a LS1 out of a 98 z28 into my '48 3100. My first question is regarding gear ratios/rpm etc. I plan on doing a mild cam, and would like to figure out where rpm would like to be when cruising for somewhat decent fuel mileage.
Using a calculator a 3.50 rear end ratio (currie 9'') would put me at 1773 rpm @65 mph (highway speeds in area). 3.25 would put me at 1647 @65, and 3.70 is 1875.

I've driven the camaro, and it has a 3.23 rear end, so the logical side of me says that would be the way to go, much more than that would probably be just spinning tires anyways due to low weight of the 3100. My question is though, would this be okay with a mild cam? I know that a non stock cam will like a little higher rpm while cruising, but not sure where that line is. Only number I came across was above 1700 is good with a non stock cam. Can anyone support this? I'm thinking 3.25's would move the truck along pretty quickly, and much more may be overkill with little weight in the rear and would be best for fuel mileage, but don't want to have too low of rpm for the engine to cruise also.

Beyond that for now, as this will be my first ls swap, does anyone have any recommendations on fuel/and or cooling system and wiring, etc.

[BR3W CITY]

What trans are you running? Thats going to affect the final drive ratio in addition to your rear gearset.

3:73 is the "money spot" for most of us running overdrive trans. Some guys like to step up to the 4:11 for accel on 'glides or trucks with long 1st and 2nd. If the camaro is a 6speed, top gear is like .5:1, so too low of a gear and your going to lose a lot of passing power on the freeway.

How mild of a cam are you considering? IF your on an auto trans, are you running a stall convertor? All this will affect your outcome.

Personally I usually consider the 3:23s a little too shallow on an o/d setup.

[jessemthompson]

Making the comparison with the camaro isn't the way to go. The camaro is more aerodynamic than the truck. A 3.23 with the overdrive in your truck would yield poor results

[Clyde65]

I had 3.08's in my truck before switching to a rebuilt 3.73 posi, I can sure tell the difference in town and when I tow anything. I could do it with the 3.08's but it lugged alot. With the 3.73's I get about the same mileage except for when I would run 80MPH, it would be 1MPG better with the 3.08's.

Go 3.73 or at minimum go 3.42's( that is what most trucks have from factory ( newer GM).

[Dustint]

The trans is a 4l60e auto. I have factored in the overdrive ratio and tire size in my calculation for rpm. I think I need to also state that I just want a good gear ratio for spirited driving and good mileage. By no means am I trying to have an awesome quarter mile or drag time, the truck will probably never see a strip, and most certainly won't be towing anything. The only reason for comparison to the camaro and driving it is that it is plenty quick to suit any spirited driving I would want to do.
Traction is going to be an issue in the AD trucks, so I don't see what the need for a stall converter would be, I Feel I would just be buying tires then. But maybe I'm wrong there?
As far as cam goes, really just after a slight power gain and a little lope to the sound.

[BR3W CITY]

Traction is an issue that is solved with good suspension and driving technique, not underdriving the motor to where it can't hurt you.

The gears your looking at are so low that you won't be doing much spirited driving at all. You've gotta consider that by setting your cruise rpm that low (and lockup is another 2-300rpm lower), your robbing a ton of passing power without a downshift.

A 3:73 on a 29" tire with lockup o/d is going to put you in a far more effect area of the powerband on that LS1 (the car motors make their power a bit higher in the RPM range, especially if your adding a cam).

Lower RPM doesn't always translate to better mpg in full weight trucks with terrible aerodynamics, as you may be actually making the engine work harder to achieve the desired characteristics.

[Clyde65]

When I had my 3.8's the lock up would never complete until I was over 65-70 which I was told wasnt good, this ( and Posi) was one reason why I rebuilt my rear diff and added the 3.73's. I have a 28" tire ( P275/60/15 BFG)

[Dustint]

I guess one thing I didn't figure in was the smaller tire size on the camaro either, It's safe to assume it will take a higher gear in the 48 with larger tires to achieve the same acceleration as when in the camaro with smaller tires? stock tires on the camaro are about 4'' shorter in diameter