I had LED lights under the bed rails of my old '97 Dodge Dually. I used Sloan LED lights from a sign shop I worked at, they were very bright. Probably expensive too, they were just leftovers from several sign projects. I ran a power wire from one of the batteries to an auxilary fuse box under the bed, then to a a pair of rocker switches I mounted under the bed rail near the tailgate. I could switch on half the LEDs with one switch, and the other half with the other, so it was partial or full lighting. They lit up the entire bed like day light. Off that fuse box, I also ran a dedicated relay and 3-way switch to power a pair of fog lights I had facing the rear under the bumper. In one position they would come on with the reverse lights, then the off position, then the manual-on position. Then lastly I used a 12V socket wired to the aux fuse block for charging my battery jump box, cordless tools, cell phone, etc. I always suggest LED lights. They don't get hot, they don't consume voltage, and they are very low amperage, plus they are way brighter than regular bulbs. Another trick in the sign world with LED's is if you want to diffuse the brightness, you can scuff the tips of the LED's with sandpaper and it'll take some of the intensity out of the light.