here are pics of my camera. like i said, my mount was meant to be temporary to find angle and all that. works perfectly so its still there.
i am pointing to a location i think would be good to mount the camera behind the bumper plastic, slightly off center though. havent brought myself to drill a hole to test it yet (new truck ya know)
This is what I did on my Ram 2500.
Drilled a 7/8 and 2 small holes for mounting just left of the license plate. Once the camera and harness was removed from my tailgate I installed a rubber grommet around the camera head for stability and appearance.

Put 2 small spacers to cover the gap behind the bumper and installed with bolts and locknuts.

Only thing is the bumper obstruction in the corner but it's not too bad as the camera is wide angle.

If I could do it again I would've pulled the camera and wiring harness out of my tailgate before assuming it wasn't removable By the looks of it it does come out but I bought $150 worth of wiring harness thinking it was necessary. Guess if I buy a new camera I'll have 2 setups; with or without tailgate.