Originally Posted by SomeStrangeGuy

I gotcha now I think, and I think you may be missing the fuses and terminals that the HD has. But yeah you're on the right track, as the primary diff between 6/7 wires is that the 7 has an extra 'power' wire to run onboard aux. equipment. From what I can recall this is usually rated no less then 20a.

BillAce may have more experience with this then I, but then again the question is not a complex orchestration of thiele-small params. rather simple 12vdc with current limiting.

Did I ask what kind of trailer yet?

...and in the end I highly recommend sourcing an all out re-kit rather the just adding some conductors to the existing. Just cleaner and neater, and since the labor is the same price