.060 over isn't too bad for a 400. As long as you have it torn down, sonic test (bout 60 bucks) would be best, also consider filling it to the bottom of water pump jackets and make sure the steam holes are open on the heads.
I have 2, one at .030 over and one at .040 over. Had the one .030 sonic tested and the report showed I could go comfortably to .060.