rear tail light wire nightmare

There are lots of different wires dangling under the bumper, Im hoping to rewire the back and splice in a license plate light. I have a wire diagram, is a wire harness supplier other than the junk yard for our trucks?

I figured out someone had a trailer pigtail spliced into the rear tail lights within the wire mess. I have the left(drivers side) tail light figured out. Trying to figure out whats going on with the license plate tail light. On my truck its on the right side. According to the diagram its suppose to be on the left rear frame rail.

Then I have this old blue connector thats not even listed on the diagram with a red wire and brown/yellow wire. The diagram shows a green wire as well, I guess thats a ground but, I dont have a loose green wire.
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Green wire is part of the ones to the trailer. I can't remember without looking, but I think the green is for the brake lights or the tail lights. Should have two separate wires for each sides blinkers. Trailers usually have a white wire going to ground or the traditional black. Easy way to do it is get a test light and a friend. Probe all the wires while the friend presses and holds the brake pedal. Mark the brake lights and probe the others with just the headlight switch on. Then mark the one with power as the tail lights. Then check whats left with the turn signal on. That way you will know exactly what goes where and without relying on a book that may not be correct or for the correct year and model.

well I fixed the tail lights and the license plate works!! The battery wont hold a charge though. It wants to fire up but not enough juice. One problem fixed more to go.. lol