To provide a little additional information. The truck came to me with a new starter yet used the old solenoid (previous owner sent the old starter / new solenoid with it after changing). The old solenoid was 4 post and wouldn't engage with the flywheel, the new was 3 post and doesn't connect to the + on the coil, but will engage with the flywheel and start the engine. The old coil doesn't have any markings on it so I couldn't tell you if it is internally or externally resisted. It did have ~2.5 ohms when tested. I bought a 12v coil that indicated it needed an external resistor but returned it because it gave me the same numbers as the old and I wasn't confident the salesman gave me the correct part.
I did reach out to one of the specialty online sites who recommended a solenoid and coil but said I didn't need a ballast resistor.
I must note again that my voltage measurements were taken with the key in the run position but without the engine running. I was told that this would make a difference.
As for the background of the truck, it sat for many years. The previous owner got it running and sent it my way. Since then I have had it running but only drove it a short ways before it overheated (should have checked the thermostat, oops). I think it also overheated the coil at that point as well but I was distracted by the blown radiator hose. The last time I had it running it just idled for ~20 minutes before the coil overheated and it shut down. The only other thing I haven't done is change the points and condenser, which I have.
Any additional thoughts please chime in. I've got a couple of ideas on which direction to go but just took the starter and old solenoid off again last night.
