Conclusion:
The GTX is all back together as of this evening. The repaired transmission performed flawlessly on the trip home, which coincidentally was the first time since I've owned the car (over 7 years) that it was driven in the rain.

The decision was also made to resurface the flywheel due to indications of premature warpage (probably came from the supplier that way). We also installed the roller input bearing in place of the usual bushing.

The Passon unit has been repacked in the original crate and will be returning to Jamie once he forwards the necessary documentation to do so.
Chalk it up to stuff happening sometimes...

The local transmission guy is apparently correct in his diagnosis and repairs to my original transmission. An extended road test once this storm front is finally gone will finalize confirmation of that.

I appreciate all the advice and help offered by several folks in this thread!
That said, I won't bother next time. There's a few bad seeds in this forum that need eradicated, sadly. Nobody needs to be badgered while seeking help and I'm pretty sure that's not the point of this forum.
Darn shame - this website has been around longer than most.