The back up light switch is either open or close to conduct the current to the light bulbs, I believe it is fed of off of the ignition switch in the run position.
I have a 1969 Dodge FSM in the shop, I'll look at the wiring schematics in the morning and add onto this reply tomorrow sometime tomorrow thumbs
My 1966 Dodge Deluxe Coronet has that same wiring in it for the back up off of the original 3 speed on the steering column minus the back up light on the dash.

Last edited by Cab_Burge; 08/26/19 01:52 AM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)