I don't know squat about transmissions. I am trusting the trans guy to check it out and let me know what it needs. I did tell him the unit shifts and drives beautifully right now and to focus on finding out the source of the mystery noise/whirring/vibration at speeds above 50mph.

I don't know if it even needs rebuilding; I can tell you all the forward gears and synchros feel great. No popping out of gear, no grinding, etc. She shifts as nicely without the clutch as she does with it, pretty much.

In other news, I had a nice conversation with Dan Brewer this morning. I called with a question and he's always, without fail, gone out of his way to help me and answer questions in the past.
Today was no exception. Real nice guy.
We chatted about his current backlog for rebuilt transmissions (2 months now if anyone is wondering) and that he doesn't trust anyone else to do them except him - and that's not going to change.
He did express some sympathy for his direct competitor, saying it was a hard gig to try to do everything himself, but that was how it was going to be as long as he did it.

I asked today about the slip yoke and whether it was possible my original problem could involve that. He doubted it (and he did remember watching my video of the noise in question) and asked if anything had been resolved about it so he could put it in his own memory bank in the future.
Nope, nothing yet Dan. Working on it. :-)