I ran two RCA cables from the back TV bumper, one went to the bumper camera, the other ended right at the trailer/TV Receptacle, to the front of the truck
I ran a RCA cable from the camera on the back of the trailer, along the frame to the front, and taped it to the trailer's plug. I put a double female on the trailer RCA plug so it can plug it in the cable coming from the front of the truck.
Both RCA cables run along the truck's frame, and come up in front of the drivers door. I drilled a hole and ran the cable up behind the panel, and to the fuse area near the left front vent. I got power for the monitor from that fuse panel (Duramax).
I see Amazon has a kit with a two input monitor like mine, might be the way to go, and just get another camera, and the RCA cable. They are cheap! Here is the link:
http://https://www.amazon.com/gp/product/B005P5UMY4/ref=od_aui_detailpages00?ie=UTF8&psc=1