Lots of places are having issues getting rear main seals to not leak. Guess it's just poor quality seals. Not taking up for Ray, just saying.
Sorry to hear you've had so much trouble w/ it. I know it sucks after making such an investment.

CHIP
'70 hemicuda, 575" Hemi, 727, Dana 60
'69 road runner, 440-6, 18 spline 4 speed, Dana 60
'71 Demon, 340, low gear 904, 8.75
'73 Chrysler New Yorker, 440, 727, 8.75
'90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt
'06 GMC 2500HD LBZ Duramax