what trans fluid

There's no "t" in Dexron, which is what Chrysler specified. But what the heck do they know about their own transmissions. If you just had your transmission rebuilt, check with the rebuilder regarding warranty if anything other than Dexron is used.

Type F (Ford) was available then, and increasingly hard to find now (Ford quit specifying it in the late 70's). Chrysler never recommended it for street use. There seems to be some sort of wives tale that it is somehow better. The supposed advantage is a lack of friction modifiers and higher viscosity. So it makes the clutch packs "grabby" and makes the converter slightly more efficient (also making the clutch packs draggy and slightly lowering stall RPM). In a street car you probably won't notice much difference other than slightly harsher shifts, maybe, but it's no shift kit in a bottle (sorry B&M). In a worn out transmission, it may make it stop slipping just long enough to sell the car, but it's no rebuild in a bottle either.

I think you'll be just fine with commonly available Dexron III/Mercon fluids. Dexron VI or Mopar ATF+4 are probably overkill unless you feel the need to pay more for a full synthetic.