Nice ride. My local mom-and-pop grocery store owner used to have one and used it to deliver groceries to the rural areas.
The carbs on those cars can get problematic and cause all kinds of cold start problems. (Remember, we are talking about a carb here) If there is any amount of grime on it, rebuild it before it leaves you set some cold morning.
The TorqCommand in that car was supplied by Chrysler it's a TorqueFlite copy , use Dexron or Dexron subs that are backward compatible.
Not just a "copy," it IS a Torqueflite (904 or 727) in a case with an AMC bellhousing bolt pattern.
You can certainly use ATF+4 if you want, it is fully backward compatible in all Chrysler automatics per Chrysler recommendation, and its a very good synthetic-based oil. But that machine is also OK with Dexron, since its a transmission that pre-dates electronic partially-locking torque convertor logic. Dexron VI should be fine- Yes, its a little thinner than the original Dex III, but its also more shear stable.