Wiring conversions are a PITA.  You can get a wiring conversion kit for trailer wiring starting at $25, a little electronic box that converts turn signals and brakes to one bulb.  I put one in my tracker, which actually had a wiring plug for it and fit, in less than 10 minutes.  It would have saved you a lot of time, using it on your bumper and for trailer wiring.
Did you build the bumper also?