would they're be any diffrence in the size of fly wheels in an S10 pickup with a 5-speed, and a Fullsize Truck with a 4 speed? i am looking for a donor vehicle and want the biggest fly wheel possible for lower idle power.:confused:

I am running a V8 truck flywheel behind my 4.3. Stock this 4.3 had an auto, so I don't know if the stock 4.3 flywheel is lighter, my guess is it would be, but I don't know for sure.

Just make sure you get the correct flywheel. Meaning, Pre-85 chevy V8 flywheels can only be used on internally balanced engines, 85+ are externally balanced. My 94 CPI 4.3 is externally balanced.

our plans are to purchase a wrecked S-10 pickup wtih a 5-speed and 4.3 to put the jeep. And we were going to use the bellhousing and cluch and just adapt to our T-18, i want to go to a bigger fly wheel for lower lugging power, will that V8 fly wheel clear the S-10 5-speed bellhousind, and will i have any problems with pilot bearings and input shaft?

Fawk those heavy flywheels. Just get better gears. The s-10 flywheel is plenty heavy.

There is something to be said for Dean's reply. You've already got it, why spend more $$? I am only running the larger flywheel because I had it, and I needed a flywheel, the 4.3 had an auto mated to it. I don't know the answer to the input shaft question for the T18, but imagine it would be similar to mating the T18 to a Chevy V8. I used a Chevy truck bell housing and a SM465 behind mine.

BTW Dean, I've got the gearing covered, 5.43s in F9s :D