I have been looking at replacing the side marker lights with LED's for sometime and adding all of the lights on the fenders and the ID lights on the back.
Step 1, replaced the side markers with a 12 LED light that was a little longer than the originals but just as wide with the chrome bezel. Changed out the license plate light with one that has 3 LED's.
Step 2, added a Thin Line 6 LED light to the fenders just above the reflective stickers on the front and back sides. Was able to run the wires in with the brake wires from the right side over to the left side where I tied them together with the left side and ran them up to the front to connect at the same point where the 7-way power cord connects to the trailer wiring.