First, thank you to Daniel Scully for the diagram and color code chart.
Even though I got everything to work in my 1976, I still printed out a copy and placed it in the book I keep in the ambulance.
The next time something stops working, that may save some time with the trouble light.
As far as wires which appear to be not connected, this is still common in ambulances built today. A standard harness is pulled in and customer selected options are connected. The wires for options not selected are still left in place.
When I restored the electricals in my 1976, I folded over and taped any "unused" wires "just in case".