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

Gus Wilson had words to say on that subject.

For awhile there was a special anti-leak rear main bearing offered for the Slant-6. Had two diagonal grooves cut into the bearing surface. As far as I know it's been unavailable for a long time, but—again—it should be possible to get a reasonably dry rear main seal with careful attention to parts selection and install technique.
That Gus guy really gets around. lol