YY 455

I have a .030 over 455 with '71 96 heads off a 400. My compression is 9.6. 6X-4 heads originally came on the 76 (I believe) 350 engine as I have two sets which I physically pulled off of 350's. They are as good as the 71 96 heads (smaller exhaust valve) and their CC's are close to 90 and the 96's are guess what? About 96 CC's. If you know of a competent machine shop talk to them about doing the machine work and you assemble the engine. There are a couple good books of info on building Pontiac engines by Rocky Rotella and way back was Pete McCarthy. Take your time with building the bottom end (double check your clearances) and follow the instructions/guidelines and you will have the self satisfaction of building your motor! A dual pattern cam --hydraulic or solid-(220's intake--230's exhaust) will work fine with a descent rear axle gearing. Enjoy the build!