It may help if you specify what year and engine code for both the 250 L6 and V8 being discussed. Both the 250 and V8s have come with both 12-3/4" and 14" (168 tooth?) flywheels. In particular, when you say "Chevy V8" there are a tremendous amount of possibilities. I'm not even sure all 168 tooth wheels were 14".
I hate to discourage anybody from participating in our forum, but we seem more oriented to repair of stock-type vehicles. You may be better-served by posting on one of the many Chevy-specific sites.