I would expect this should work. The lights shouldn't be switched through the ground. Given the short distance to the rear, the same size wire as is already on the mudflap lights should work fine. If you are a worrier, go a size bigger. Sorry, it has been a while since I saw the mudflap lights, so I wouldn't even venture a guess as to the wire size. With luck it will be marked on the wire. Otherwise, try to match it up, or use a caliper to measure, then look up the gauge size in a table.