I used all three sizes of flywheels on my 1970 Hemi Cuda with two different scatter sheilds when I raced it in NHRA stock, the smaller diameter and lighter flywheels work better on the small nine inch tires we had to run, no problems running any of them with headers in the car, the starters where hard to change with the headers Make sure your bellhousing is compatable with the starter and flywheel size It(flywheel size) does make a difference on the stock type bellhousings, not so on the scatter sheilds, except for the early Ansen scatter sheilds