Deck height: I wish I could find it in my notes but I spoke to Steve Weiner about deck height once and he said that he doesn't like
more than 40/1000" (1mm) because detonation starts out in the "pocket" near the edge of the piston. I hope I'm remembering that right. Hopefully Steve will chime in.
Base gaskets/shims: You don't mention what the motor is. When I was looking for base gaskets a while back Stoddard had oversize (>.25mm) gaskets for pre-Carrera's but only normal size ones for Carrera's ('84-89).
Competition Engineering advertises that the have a wide selection of cylinder base shims.
-Chris