hi Mike most likely your voltage regulator reverse current relay failed to open which disconnects the generator from the battery when you stop the engine .
Otherwise , battery current will run into the generator and try to drive it as a motor . As it is held by the fan belt , cannot turn it will burn up .
.So likely nothing was wrong with your generator but it is burned up ( likely armature ) now .
Has anybody been inside your regulator lately ? Normally that function is very reliable . This usually happens if someone presses down on one of the relays , the reverse current one, it locks in if you do . Only way to release it , if it happens is disconnect battery . Of course it is possible the relay spring fell off / broke or the fine wire coil corroded open . There are two windings on the reverse current , or “cut out “ relay one for voltage ( fine wire) one for current ( heavy wire ) —- when the current reverses in heavy wire ( = discharge at engine stop ) it fights the voltage coil magnetism and it pops open ; when you start the car it is open still , but gen volts quickly build up , pull it closed , charge current adds to volts magnetism pulls it even more closed . Until you stop .
So Get new VR , dont just replace gen , as a new one will burn up too . Check harness wires for melt too . You are lucky you went out …
Can lead to harness destruction
Ammeter tells you all this .
I would get a used gen , keep F stock, Murray Park etc , just get new brushes , you are good to go Many if not most 35 A dodge Plymouth chrysler 57 60 non AC have same parts inside , watch number of grooves , — of course best to get one the same , they can be clocked differently for F mount , send him a picture
hope this helps ,
John
I returned from a cars and coffee event this morning, parked my 300F in my garage, and it was running fine. About 30 minutes later I went back to the garage to get something I left in the car, and the garage was full of a whitish gray smoke. I opened the hood of the F and the generator was smoking heavily. I checked the battery and it was at 10 volts and would not start the car, I put a battery pack on and the car started but the amp gauge pegged discharge, so I shut it off an disconnected the battery.