Using a 57/64" hole (I would definitely bore, not drill) would give you a 72% thread which is right around where you want to be (in the 75% area). If you want to up that a little bit, just make a smaller hole. Here's a good calculator that will do all the thinking for you:
http://www.newmantools.com/tapdrill.htm#callink The thing you just have to watch for is that concentricity is a must for the bore/barrel threads. Try to do all the bores and threading all in one setup to ensure concentricity.
All the rest of the threads (including grip frame) should be fine after anodizing. If you want to be careful about it, use an H3 or so thread limit and that should allow you plenty for the anodizing thickness (only about 0.0015" thick for Type I anyways).