A while back, I followed Virgil's advice, installing those lights he recommends above, in the step bumper of my 1986 F250 - after buying new tail lights and putting #796 bulbs in the small factory reverse lights. I then installed a manual switch with heavy duty wiring (I used a pull switch with bright indicator, mounted on my floor shifter, so anyone who recalls driving a 1940's or 1950's medium truck with two speed axle will have a flashback). This has worked well, and has the added benefit of the switch with HD wiring eliminating voltage drop on the factory wiring. I can see the lights get brighter when the manual switch is closed. I have decent light for hooking up a trailer or working behind the truck, when out in the woods at night.
I still have plans to augment the stock cargo light with floods atop the cab guard, along with some side floods, but these will be separate circuits. All of this is on an old truck that actually does get used to harvest firewood and yard logs in a selective logged area, so appearance is not an issue.
I rewired my 1988 car hauler trailer before LEDs caught on, and the job has held up fairly well. But next time, the trailer definitely gets four of the lights Virgil recommends, in place of its incandescent Trucklite reverse lamps.