The Passon transmission was installed at the mechanics' shop this morning, myself assisting with the install.
Everything went back together fine but all hell broke loose on the test drive, which went all of 100 yards before an awful noise akin to what a starter sounds like on a small block Chevy when it needs LOTS of shimming.
In 1st or 2nd, it could be stopped by pushing back in the clutch; in 3rd it made it regardless of whether the clutch was in or out.

Got Passon on the phone and he requested to hear the noise, which I reproduced for him "live" while on the lift again.
The mechanic, who is knowledgeable on manual transmissions and has rebuilt many in his time, was under the car and pinpointed the issue to the 3-4 part of the transmission. Manual operation of the 3-4 shifter selector on the side of the transmission revealed pretty crappy, hard to operate.

I received what can honestly be described as a negative attitude over the phone, which was very disappointing. I'm into this transmission a good chunk of money; I don't need poor attitude and service, which is what occurred.
He's supposed to be sending me another one.
We'll see, but a wholly disappointing day, capped off by negative attitude over the phone. This isn't going well so far.