How are all of your grounds? Mopar lighting seems to be the step-cousin to England's Lucas... Start adding temporary grounds to your lighting circuits one at a time and see if that helps narrow it down. I've owned several trucks, and all of them needed an additional harness from the exterior lights to the neg on the battery to operate efficiently and effectively. You don't need to get that crazy yet. Just make a big jumper to attach to the neg terminal on your battery and touch the other side to your fixture.