A heavier (30 lb. or so) flywheel will give you better take-off, but will take longer to build rpm's. A heavy truck with oversize tires or high gearing would benefit from the heavy one. A heavy flywheel will have more inertia for taking off, and therefore have less rpm drop between shifts. I think the one I was using was about 27 lbs., and that was stock for a 305/sm465 with 3.08 gears. It depends on so many variables which one would work the best for your application, but I would err on the heavy side given the information that you have provided.