Doug , my megablock was rehoned a few times and was 4.5043 when i put it together to build the 550 cube combo last year. I still had to file fit the rings quite a bit. I calculate that i could have gone out to 4.508 and still get .025 end gaps using 4.505 rings. Or you might be able to go a bit bigger with a gappless top? I had my 4.500 pistons coated by line2line if you remember. No sense taking your block out to 4.530 if there is a way around it.