If you have a FD damper on hand that fits your application then I'd use it. It should work just fine with a 4.15 stroke street engine. I wouldn't use a FD on a circle track engine or a high winding drag engine but a stroker street engine should be just fine. FD are really designed for diesel engines and truck engines and such but they seem to work okay on passenger cars too. I think it is very important to have the rotating assembly properly balanced regardless of which damper you use.