You have to know where you are starting to know where you are gonna end up. At the moment you are just doing a pure guessing game. Measure a head, KNOW what the volume is. Cut .0048 of an inch to reduce the chamber 1 cc. Mopar engine book and Larry Shepard of "How to Hot Rod Small Block Mopar Engines" state that for every .010 cut from chamber face, cut .0095 from the intake face.
From what 318willrun says, he's had good luck not cutting intake face, no reason to doubt him, so maybe you won't/don't have to do that. Time will tell.
Good luck, have fun.
