Originally Posted by 71fj40guy
If I mod the heads and raise the compression ratio or get new 64cc heads will I still be able to run normal 87 octane unleaded?
Probably yes, the static compression ratio even with 64 cc chambers, with the original pistons, a .025 inch stock deck clearance, and a .020 thick gasket only generates 8.4 to 1. For a Vortec style chamber in cast iron this will easily operate on regular unleaded especially with the stiff gearing you've got.
You're far away from compression requiring premium unleaded with this engine and its original cam. To get into compression ratios requiring premium fuel you'd need to change to a flat top piston along with small chambered head.