It's hard to say if a complete rewire is necessary, Can't see what it all looks like. Remove all the cut wires. Follow them. See what they used to do. This will help with knowledge and confidence. Read the tech section here to see what should have been done during 12V conversion and see if it all was done.
1. Ballast resistor
2. VR or no VR
3. 12V bulbs
4. Voltage reducers where required
5. 12V coil
For me, a 12V conversion would include a new fuse panel. This would eliminate fire danger. I don't think you have any fire danger but fuses are really the best idea. For my trucks, which I don't drive a lot, I always take off the neg battery cable during parking at home. Not that I can't wire properly, I just can't sleep properly.
These old truck designers were not hip to fuses. Add them to everything as you go. Wiring, in general, is the same up thru and past the 70's. So study a 60-66 diagram or 67-72 diagram and see how a fuse panel is wired as well as the rest of the trucks. They just used more connectors and, as said, fuses. The foot start vs solenoid is also a difference, but the same idea.
You can, of course, start over using a kit with a prewired fuse box. That is not hard with our trucks because there are not that many wires. The kits are divided (by you) into bundles for the various "systems". Routed, cut to length and terminated. Easy.
Bundles from fuse panel.
1. Starting and running and charging
2. Gauges and gauge lights
3. Front lights/dimmer.............. turn sig if present?
4. Rear lights/stop.................. turn sig if present?
5. One-off, or switched single wires, like: horn, lighter?, radio?, dome, wiper?, heater motor and a direct hot wire or two (fusible linked)
The light switch is involved with some of 2, 3, 4, 5
The grounding portion is not included in the kits. That would be mostly the metal of the chassis, motor and body. This is very important to the job.
It is a part of wiring that never gets proper attention by beginners.
