On heads, you can gain by smoothing the roughness of the casting. Rough areas will cause hot spots that add to predetonation. Aka KR.
Smoothing them and milling the valve guides to accept a higher than stock lift is what is considered a stage 2 head.
If you smooth, port and add bigger valves, that'* a stage 3.
IMO if you don't have headers, and plans to go well into the 12'* you won't need to port them much. Go for smoothing the roughness.
I didn't do any heads. Got a set of stage 3'* at a great price and dropped them at a machine shop to be checked.
00 Regal GS: All kinds of cool stuff.