How much milled off heads to raise compression

You can usually mill the heads quite a bit as long as you take the proper amount off this intake. I'm guessing later heads may be thinner but my ported "J" heads when I had a small block were down in the 60-62cc range after getting chopped and worked quite well on my 360. I'd see if you can find someone who's played with later model stuff. One of the head porter's out there. They typically know how thick decks are, etc.