Here's an update to how I handled this. I originally wired up the tail light cable from the camper to a four prong plug that matched the factory tow wiring plug. This worked for our first two trips but I did not have the backup lights as there is no connection for them through the factory tow plug - pictured below. My original idea was to redo the tow plug with a five prong unit that I could tie into the backup light circuit. Two things I considered about this - changing the factory wiring and laying on my back under the truck. There was also the distraction at night of the light from the truck's tail lights shining on the inside edge of the camper. So I got to looking at the factory wiring harness at the back of the vehicle.
