Sounds like you probably got a hp 390 (375hp)------porting /polishing the heads won't help you much and because of the unleaded gas these days is a waste of time/money---
if the cam doesn't have any flat lobes/or musrooned tappets and rocker arms are adjustable, just freshen the hone/rings, bearings, timing chain set the valves to .027 for that wonderful tappet music, 38 degrees total timing and go kick some butt