My brother and I both use their strokers kits. Mine is a 440 block (493) and he uses a 400 block (499) and both have been raced and holding up fine. Some of their other parts I have heard can give problems like their rocker arms but I have only used the stroker kit as my heads are Indy EZ heads. Myself I would have no problem using another of their kits but I did check it over real good. Other then tight piston pins which I honed the rods everything else checked in specs. Ron