Stock 318 head chambers are 68 cc while .040 milled 360 head chambers are 65 cc. I fail to see where the drop in compression occurs. The 360 intake ports flow 190 to 200 cfm up from about 170 cfm for a 318. I would not mill any more than .040 and you mill the intake side of the head, not the intake manifold.
You remove .0048 from the head surface to subtract 1 cc from the chamber on 340 / 360 heads. Chrysler Racing manual and from my experience is dead on.
If you are not changing heads why bother changing head gaskets? Just use the Performer intake, 4 barrel carb, cam, lifters, valve springs, and tune that rascal in. Add Dual exhaust and be done. Maybe a 3.21 or 3.55 gears. One thing at a time so he does not get overwhelmed.
