As I mentioned in another thread, if you have a rope rear main, one of those bottled products by Bar's Leaks (or similar) that claims to "fix rear main seals" do indeed work. They simply swell the rope seal, and do not affect the oiling system.
The rear main is always a thorn in the side of proud Pontiac owners. But rear main seals rarely leaked on a factory assembled, never-been-apart engine. The leaks started occurring when rebuilders did not install the rope seals correctly, and then of course later there were all sorts of whiz-bang rubber/silicone/molded products supposed to free up 5 hp, and they leaked like crazy.
A Buick friend of mine calls a stain on his driveway "The Mark Of Pontiac" (reference to the Mark Of Excellence) because his friend's 71 GTO always leaves a dime-sized spot of oil on his driveway when he visits.
