There is a coiled up wiring harness on the frame just behind the cab on GM trucks to install in the box of the truck for fifth wheel and truck campers. Put that into the box and hook up a 7 pole female plug to plug the camper into, and then the plug on the bumper is good to go for your boat.
On my 2014 I just popped out the plastic cap that GM put on the front wall and fed the wires through put the receptacle on the end of the wires because I couldn't bring myself to drilling a big hole in the side of the box to mount the plug into.
Brian
2014 only has 7 pole plug at bumper.
