I have more questions than answers;
1. Is that a condenser on the generator or a cut out relay?
2. Is your new wiring harness designed for a later voltage regulator (with three contacts for voltage regulator, cut out relay and current regulator, like that shown in the wiring diagram linked above)? Or is it designed for just a cut out relay like you would have for a 1937 truck?
3. Is that a headlight relay in your second picture on the firewall (and not a voltage regulator)?
This time period was one of transition from having just a cut out relay (1937) to voltage regulator with cut out (1938) to addition of a current regulator (1941, I think). So, no telling what you truck might have in terms of modifications at this point. You need to figure out what you have on your truck, and what your new harness is designed for.
Kent
