I did this on my 2000 Ram and just had to do it again for the new beast. The install is pretty easy, but time consuming and requires some soldering skills, and electric drill and some hand tools. Total spent for this mod was about $65 for the lights, connectors and wiring supplies. Total time was about 4.5 hours.
These are the lights I purchased from an eBay seller in Hong Kong. Took about 8 days to arrive. The nice thing is these are encapsulated in clear silicone to make them waterproof and they have 3M adhesive on the back. The roll is about 15' long, but I only needed three 3' pieces for this project. The rest will find other uses.
I always mount an accessory receptacle in the back corner of my trucks. Makes it easy to connect a 12v compressor, vacuum or other 12v device when working away from the interior. This one is made by Bell and can be panel mounted for a clean look. Also has a rubber cover to keep the elements out. It cost $9.95 at Autozone.
I made this harness for the 3 light strips that are mounted to the bows from my cover. The connectors are Radio Shack items while the corrugated sheathing and anchors came from Advance Auto. This gives the harness a clean, factory look and allows quick disconnection for whenever I need to take off the cover and remove the bows to load something in the bed.
Close-up of a connector.
The plug to power everything is a standard cigarette lighter-type plug. I connected the socket to the running light of the left taillight assembly. I prefer this to having it be hot all the time so that anything plugged into it can't be left on inadvertently.
The lights off.
The lights on. You can't tell because there's a lot of ambient light, but in the dark they really light up the bed. Makes finding things back there at night a lot easier.