Trailer Wiring with US rear Lights

[Rippers]

Ok I have the Tow bar, ordered another number plate and found a 7-pin Hella tow socket and hopefully got a lead on a actual westy trailer

So.. wiring time this seems fairly straight forward using the graph below and its basically a 7 core lead spliced into the wiring in the engine compartment

...but I would like to retain my all red rear lights so how would I go about wiring them? I had though about rewiring the the rear reversing lights into indicators using silver/amber bulbs.. will I need add a reversing for an MOT thou?

 

[Max Power]

Reverse lights are not required for mot.A lot of people with u.s busses put amber bulbs in the reverse lamps,me included.I would use piggyback spades on the rear lamps to save cutting into the loom,no scotchloks please