The Firestone RH5° rims (specifically) are no joke - a quick search of this site and others will lay it all out along with possible potential replacement options. Basically the locking surfaces rust away and create a dangerous bomb that can go off at any time, but can be additionally agitated by inflation attempts drastically harming the inflator giving them the moniker "widow makers". This term unfortunately has been incorrectly adopted to describe all split rim types by some, hence the misapplication of information on their levels of safety. Firestone RH5° rims should not be in service. Other split rim types can be used appropriately in addition to more modern tubeless single piece types.

 

It sounds to me that Grandpa pretty much made the conversion to 12 volt, albeit incorrectly. My 51 F1 was also poorly converted, using a cheap kit with all unlabeled red wires. I tore it all out and started over, and because the PO had already spent money on Autometer gauges, an alternator that looked like a generator, etc. I stayed 12 volt.

There are lots of good wiring kits available. The good kits have the wires printed with the circuit or numbers to keep track of what goes where. Stay far away from the cheap generic kits sold on ebay and other places, as they are poorly made, with low quality wire, insulation, connectors, etc.

Do a search here on wiring and you will find tons of good advice. Search for wiring diagrams to get to the details as to how things are wired. You can search for the overall diagram, and also for specific areas, for example, how the ignition switch is wired, or just the horn, starter, etc.

Take your time and don't let the frustration get to you. Ask questions, as many of us have been through it and are willing and able to help.

 

Great advice from Hulley!
A very knowlegdable guy here is Ross, Albuq-F1. He posted a schematic in the thread (linked below) some time ago.
Have your daughter follow the link, scroll down to post #3, and ask her if she could print the pictures that he posted. You will see one diagram labled 48 to 49 F-1. Its really about the same as you will have except you are currently 12 volt. As long as you have the 12 volt components such as the battery, generator/alternator, voltage regulator, lights, voltage reducer for the gauges, firewall mounted starter relay,etc. I would just leave it 12 volts and clean up the wiring. Depending on the coil you are using you may need to add a resistor between the ignition switch and the coil itself. Maybe your Grandpa already had that since it sounds lile you already had it running. Just like Hulley said, take you time, get a good 12 volt test light, and focus on one circuit at a time. You will really enjoy driving it one you have it all done.
By the way, a lot of times previous owners get creative with the wiring, like maybe changing start buttons over to key start etc. If you find differences and they seem to cause confusion, please let us know what parts you actually have and we can help you through that.

https://www.ford-trucks.com/forums/1...951-f-1-a.html

Happy Fathers Day!