Continued inspecting and tracing the wiring. While reviewing the wiring, encountered some wiring that ran ahead of the firewall. Looking at it I was able to determine the original location of a few more pieces on the firewall.
Tested the original starter solenoid. After 40 years of no use, it still works perfectly. It was covered in grease and dirt and grime so I spent some time to clean it up. It won't make it work any better, but it looks nice now.
Pulled some of the Jeager connectors apart and traced the wiring. Cleaned the connectors for reuse.