Tailpiece, and possibly the rear mainshaft, will not bring joy to you. If you found that one, and a junker 4wd R151, you might have some joy by transmogrifying them together.

Holy cascading quote boxes, Harry! That's interesting. Mine pulls pretty strong, though I do have a 4.7 gearset in the rear tcase. Lots of times I do run the stock gearset in the front though. Maybe I'm spoiled? But it pulls great on the street! Almost, barely, as if, geared a tad too low. Not enough to plunk down cold hard and tear things apart though, and when towing it's nice.