GM to Mopar trans swap?!

You got it.
I learned to call that part a mainshaft, in the tranny shop I once spent years in.
You learned to call the same part a tailshaft.
Same part.
Now, How in the world did you do that?! And with a teener no less. I needs me summathose traction bars. Heck, I need that engine. Bring me that whole entire car, dogonit! Right now!.......................lol
Usually the rear end lets go first .