What about using lights sold at big rig shops, the ones used on semis and towtrucks ? Those are usually durable, can be had as one big lighthousing or multiple lamps that you arrange the way you like. You can get those as incandescent or LED, flushmounted or fitted on the back of the bed, square, round, oval you name it. You could use most of your OEM wiring but you'll need to splice the lights and probably lengthen or shorten the wiring to best suit your mounting location and wire routing.

I would also mount some worklights/tractorlights on the back to act as back-up lamps and to light up camp at night. You could relay them via the reverse lights and to a switch, so you can either turn them on or they turn on automatically when you reverse.