Is there any way to PERMAMENTLY eliminate rear main oil leaks?

Realgaskets is the bomb. I use their gaskets for not only my big block oil pan (with the windage tray) and the 727 pan. No leaks from them at all! Great folks to work with too.
I'm a big fan of their silicone garden hose (=washing machine hose) washers. That's an appropriate application for that red-orange silicone material they use. And yeah, they're great to work with. But I've seen too much incompatibility of their apparently one-and-only material with too many applications to get onside with their idea that it's suitable for whatever one is trying to seal up.