i put ductile iron main caps and ARP studs in my 512 motor with the iron heads, the first inspection after dyno testing and some street and strip driving, not a lot, I found similar results I file them flat and put it back together, I swapped heads also and ran it the next year a lt more at the track and on the street. I looked at it agian the next winter and had a little main cap wlaked, not near as much as the fsrt time. I swapped the 4.250 stroke crank out for the 4.300 stroke crank to increase the compression from 9.25 to 1 to 10.29 to 1 by moving the pistons up from -.025 to zero deck I had all the main caps off that motor at the begiining of last year and I didn't need to file the caps anymore, I leak it down last month and put it on the dyno, it made 728 HP on pump gas at 4300 ft. elevation I put it back in the car for another year of playing Same main bearings for five years now