When I got my short block (Mopar Mega block, 4.5 Mopar crank from Indy) it only had 18 passes on it since freshened. I tore it down anyway and found the thrust torn up. Crank even showed a little heat. After talking to the previous owner he said he had a converter issue. I polished the crank and put it back in. It had the tightest crank end play I've ever measured, .003". It's been in the car for 200 passes. Just pulled the pan to check the bearings. Thrust looks like it came out of the box. My bet is converter.
Doug