Speed Pro makes a hypereutectic piston for a 383. With a flat top piston (zero deck) and 64cc heads you would be in the ball park of 10.0 compression. You could fill up at any pump. I have had my 64cc head milled to 60cc and one terrible afternoon I realizing I had forgotten my fuel jugs at home. I stopped at the gas station and fueled up my race car with 93 octane. I had no choice. It ran just fine. I race a small block chevy that can turn 8000 rpm's but usually runs at 7400 most of the nights. I run Speed Pro pistons. They cost an 1/8 Of JE's and I have never had one fail. Use this info as use wish.

Jason