Who says you can't run headers? You just have to get the right kind (D-port headers, not round port). 7k3's --- big valves (2.11/1.77), screw in studs, and 96cc chambers (nominal). Put those on a 461 with flat top pistons, run a 0.040" compressed thickness head gasket, zero deck the block, and you'll be at 9.517:1 static compression ratio. Add a cam with some attitude and a 'later than usual' intake closing event and that's dang near perfect. Flat tops and zero-decking will give you good quench area for lots of turbulence and minimal exposed edges in the chamber --- both very good for detonation resistance.
If you're going to run iron d-ports on a big inch Pontiac, that's about as good as it gets.