New addition to the stable - 83 Ramcharger - questions, too

Ahh yes the good ole' Ramchargers. My first car was a 1984 Ramcharger Prospector III package, it was equipped with 4WD, 360 and an A/C that worked until they outlawed R12 refrigerant. And I was a poor High school graduate who couldn't afford a retrofit to R134.

You most likely have an A727 automatic. If you have a manual in, it would be a NP-435 4 speed.
The rear end would most likely be the 9 1/4.

Aftermarket repair panels is not very common for these things, you might have to cut out a good one from a junkyard or parts car.