My factory installed rear view camera is on the tail gate, not at the cargo lamp... I assume that all the wiring is in place and you can install a unit....
However my neighbor just bought and had installed a upgraded radio and rear camera by a aftermarket supplier on his truck (Ford) and it fits the exact dimension in the dash and is seamless installation... very clean, very nice, great picture from a camera located on the license plate frame and LOTS LESS than the factory FORD kit he was looking at..