I have not had much rear main seal luck with big blocks in the last couple years. Stock retainer and 3 different seals, all leaked. Thinking maybe the crank but it shouldn't leak as bad as it did with a few thou taken off the seal surface. Then my dad had a beeotch of a time with a stock 383, leaked like crazy. Never had problems until the last 2 years or so. Mine leaks just a little but that is still too much for me.........I'm sick of changing rear mains though so I live with it for now. Doing this twice on the floor inside of 50 miles of putting the new engine in gets a bit tiring.