Tony I milled the 452's .060 that were on the 383 that was in my boys Dart a few years ago. I also milled the intake side about the same amout. I had no issue's at all and everything fit fine with no leaks. I also milled the 906's on the 440 in my 63 .060 and I can tell you the chamber's went from .085 to .090 deep to .025 to .030 deep. I also had the intake sides milled and they fit fine. No leaks yet. I myself dont like to go much more then .060 as then it starts getting into fitting problems. Course when cash is tight we have to find cheap ways to raise the comp. This pic is after I had my 906's milled .060. Ron