Good. Stock heads have an incredible amount of variance, even if they have never be resurfaced. Do it correctly, or don't bother at all. The advertised compression of a piston is also usually nowhere near what you end up with, as it is that compression with blueprinted heads.
If you are going through all this trouble, please upgrade the oil pump, and probably the drive, as well. (not too up on AMCs)
Michigan- The Only
Great Lakes State South of the Mason-Dixon Line.