340 build

Shouldnt my compression be around 9.5-8 with .020 milled off the heads and a thin gasket? Do you think I will have clearance issues with that?

I doubt you'll have clearance issues, but you should check the P/V clearance after all the final numbers are in and depending where the cam is degreed to. The guides will probably be machined for a dual spring and the appropriate seals so i dont see a clearence issue there. Just looking at generic numbers, i think the 9.5 comp is easily obtained.