Not 100% accurate but a very good clue is to check the bulbs in the car. If they are 12 volt bulbs then you most likely have a 12 volt system unless the job was started and never finished by someone. Was there a battery in this thing? Was it 6 or 12 volts? I'm not familiar with all the parts swapping that can be done with the Mopar flatheads but it may also be that all the 6 volt flathead stuff will fit right onto a later flathead that ran 12 volts.
This might give you some idea what you have until you get a chance to accurately verfiy the generator, etc.
