im chasing the same demon you are, only the rear seal in question is new...one question... what year block do you have? mine is an 85, which uses a one piece seal. does yours leak down onto the bell housing, then onto the ground? or is it around the pan rail. IF it turns out to be a pan gasket, do yourself a favor, spend the extra bucks, and get the one piece pan gasket... that way, you have one (actually three) less places for the oil to leak from. as far as the leak stop question, that stuff is basically lacquer thinner, it might work for a while, but i feel it would make all the seals brittle over time, and instead of replacing the rear main, you are replacing all the seals in your engine.