Their are only four places oil can leak at the rear of the motor, above the main seal, oil galley plugs and cam plug, oil pan gaskets, the main seal itself or the main side seals shruggy
I use adhesive silicone to seal the side seals after the main seal holder is installed, I also use a very thin strip of that adhesive on top of both main seals so they seal against the seal holder and sometimes a tiny dab on the seal ends where they touch. I use a putty knife or a wide tip thin screw driver to smear the silicone into the gaps on the seal holder to the block, it is not easy but I do it so you can to wrench scope
i build lots of Mopar B, RB and 426 hemi that don't leak oil from the rear work shruggy
I hope this helps up

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)