The harness itself is under the dump bed, there is a connector just to the rear of the engine along the drivers side frame that you can tap into if the whips are stationary. If you want to get to the actual tail lights in the dump bed you need to remove the colored accent plate / general logo on the upper side of the fender. There is just one bolt on the leading edge of the bed, the rest is plastic tabs on the top and rear. Roll up and our carefully and it should pop free. That will expose the upper bolts to remove the fender. There is 5 or 6 bolts under the upper lip of the bed that you need to remove along with 2 screws by the tailgate latch and 3 or 4 on the bottom of the bed. You can then remove the outer fender and the light harness will be right inside.
