1939 pickup solenoid

[CP]

We bought another 6v coil and all was fine and installed with the "+" to the distributor since truck is 6v "-" ground. Truck solenoid started clicking recently. I have been unable to find a wiring diagram for a 1939 pu. Van pelts does not show. All part suppliers show the solenoid as a 3-post. The exist solenoid that appears to be junk is a 12v 4 post that appears to been converted to 6 volts somehow by "markings". Evidently this converted solenoid is toast since it got really hot and started smoking.

The questions....is there a wiring diagram for this truck? 1939 pu (was a fire truck).

Solenoid part numbers based upon a couple reputable suppliers are:
01A-11450 (steel Ford Script) and 21A-11450 (Bakelite Ford Script).

Both Solenoids are available and are "3-post".

After removing old 4-post converted 12v with the "correct" 6v 3-post, what to do with the "extra" wire.

Upon reading, the extra wire appears to be a ground, yet being "+" ground, I am really confused.

I plan on starting the truck by bypassing this solenoid entirely to make sure the starter is working. After that, I could use some guidance.

CP