As with many other subjects, this one recurs every few years as well. Besides what you went thru to date for a metal bear swap, there is an electrical oddment in the way the headlight gearbox was originally installed. Specifically, that plain DC motor MUST run ungrounded to be reversible. So for unknown reasons, the single, short power wire into the motor case is factory supported at the end of the motor by a special Bakelite support stand-off for a spade lug normally used to ground wires.
Except in the case of a DeTomaso! If the tiny Bakelite insulator/support ever cracks or is damaged, it will attract road moisture and provide a ground path, which can inactivate one side of the reverser arrangement or even blow fuses "for no reason." And your headlights will not come up, or maybe not go back down. I chased this for a whole wet Saturday on our Pantera.
The simple "fix" is to unplug the power wire from the sensitive insulated spade lug and plug the motor wire directly into the power feed from the stock wiring loom. Then well tape or shrink-wrap the connection. Support the loose wire with more tape or a zip-tie around the motor case. Thats it!