Call the tech lines for Crane, Crower, Lunati, and CompCams. They will want to know the details of your car, your engine (I would recommend going 383) and see what they recommend. Choose the one that is closest to the average of all four. And I would recommend forged pistons. They are not just for racing. They may cost a little more, but they are stronger and lighter than cast/hypereutectic pistons. I used SRP forged pistons in my 383. Given you are using 64cc combustion chambers, you will want to look for dished pistons to keep you compression around 9.5:1. Check out the rotating assemblies like SCAT or Eagle--they are a great deal.