'75 A model 8.25 worth upgrading or leave as is?

Yes, all 8 1/4 2.73 and higher carriers are interchangable up to 1996(splines changed from 27 to 29) ,also 76 and newer uses larger carrier bearings so if you want use a 76 up carrier you'll have to swap to the smaller bearings.

HaHa!It never fails with my luck on stuff like this.I was just 1 year away from having the carrier without the head aches.
Thanks for confirming on the interchangeability.