I just bought a used Eagle truck cap for my '05 Super Duty (8 ft.). The current wiring on the cap is a flat 4 trailer harness that connects to the cap's 3rd brake light and the interior light. If I get another flat 4 and use the mating half, where do I tie into for power? I don't want it to look like a cobbled mess. Any help on nice wiring tips is greatly appreciated. My truck has the factory trailer wiring.

Thanks,