Looking thru my new purchase 1956 F100 and there are many surprises and mysteries. I believe this truck is a mismatch of 2 trucks. A 55 and a 56. I think the 55's had 6 volt and the 56 was the first year for 12 volt. Is that correct? Also looking at the 56 service manual it looks like the black cable directly off the battery goes to the starter solinoid, and it shows the other cable going to ground. Red? Positive ground? All the wiring is in a crate and all the dash switches,etc are all disconnected. And help will be appreciated. Thanks, Greg.

 

You are correct. The 55 was 6v positive ground and the 56 is 12v negative ground.
The guys with the 56 wlll be able to give you more info on their wiring.

Take some pictures and show us what you have. What are your plans for the truck.
There is a lot of info on this site about wiring. You can spend hours searching through threads.

 

You are correct that 55 was 6 volt positive ground and 56 was 12 volt negative ground. The polarity doesn't know anything about wire insulation color. Depending on which pole is grounded, the opposite one goes to the starter solenoid from the battery.

 

Thanks guys