Well, an update of sorts...

Weather has been downright New England-ish the last couple weeks and we have still more to come apparently. Anyways, I seized on a few hour window of opportunity today and ran the car over to the shop.
Fellow took a ride with me, heard the noise clear as day - and looked at me and said "I've never heard that before in my life".
I thought --------
He went through all I had done and came up with the conclusion that, based on what he was feeling/hearing in person, it could only be a bearing.
Reckon I concur at this point - the noise is getting worse with more driving and the gear lube I drained the other day to remove the speedo pinion didn't look so great, adding credence to the bearing theory.

Thought process quickly moved from there, past trying to fix this one (which would no doubt turn into a full blown rebuild quickly) to ok, guess I'll have to fetch another transmission - and if I go there, it won't be just any transmission.
It best come from a known good source and either have a warranty (hello, Passon or Brewer's) - or come from someone I seriously trust to get it from.
Only going to do this once. Really don't have the patience - or yes, time - to fool around with this for long.

Oh, and the real shocker of the day - he doesn't want to do the swap, either. He tells me this as I make note of the '71 'Cuda on one lift and the full tube frame 'Cuda in another bay.
He says he only works on his own Mopars now, not anyone else's - and "modern" stuff for customers. Says something else could go wrong during the job and he doesn't want that grief.
Whatever...
I got a couple other places in town that didn't bat an eye telling me they're not afraid of the job and they shouldn't be.
The one literally within a mile of my place says "yeah, bring it by or I can come give it a nice ride on the rollback. $100."
As in he wants $100 to do the job. Even expects me to be there when he does to "keep him straight".
I think I have a new buddy. :-)

Ok....Brewer's or Passon?
I'd love to do an 18 spline, but my brand new clutch setup is for a 23 spline 11".