Did you have any luck with the wiring diagram? I am installing parking sensors witch attach the the reverse light, but as the light is located in the tail gate is difficult to easily access the light fitting. I have looked at the connector located under the rear right hand side where the factory fit towbar connects to but no joy there. There is a junction box located behind the left side panel in the boot but unable to decrypt what each cable is
so a wiring diagram would be handy but I can find one.
I am also considering a towbar but the Ford option is rather expensive, where did you get yours from?