would need to know if this trans is a RH or RE model.. RE unit would have a round electrical connector at the case 8 pins.
RH would have a 3 pin connector , usually oblong shape.
RE trans not shifting I would suspect the electronic governor pressure control.
Were the electronics replaced during rebuild?
I have many problems with aftermarket electronics on Mopar trans.. I only use the OEM stuff, especially the governor pressure control
Dont worry how old you are... it is the mileage on your body that adds up.