Here is what the wiring looks like on the firewall. Someone did put a Ford relay switch on it, though. Don't mind the broken fusible link. I did replace that.
Chrysler used those at least through 1960.
Sometimes used with battery in the trunk wiring.
But yes the questions now are how is it wired? Why was it wired this way? and is easier and better to just wire it like a '66. Chrysler type relays are can be readily purchased.
The advantage of that type of heavy solenoid relay is when a heavy current has to pass through it.
Normally the big battery cable attaches to one of the big side lugs, and on the other side is the big cable to the starter. Ford Starters don't internal solenoid relay.
One of the side lugs connects to the trigger from the start switch. The other is often used for the start circuit bypass of the ballast resistor or resistance wire. NSS connection is on bottom, if present at all.
