GT40P headed 306

[MiracleMax]

I'm screwing together a GT40P headed 306 so we can put it in my brothers 86 four banger.

I've got a few questions about the heads.

They are unported P heads with the stock valve size. I'm using Manley SS race flow valves but i'm not sure about what type of valve job needs to be done? I've heard that a 3 angle valve job might actually hurt low-lift flow?

Anyways here is the combo

Holley 670 CFM Avenger carb
Edelbrock Air Gap RPM
GT40P Heads
Comp Cams Extreme Energy 274 (302 firing order flat tappet cam)
9.5:1 comp
Stock length rods
1-5/8 Long tubes with 2-1/2 X-pipe and bullet mufflers.

The engine is gonna be backed by a C4 and a 3.55 gear