The worst thing that can happen is that an engineer worked on the motorcycle.
Sorry engineers but engineers just have a knack for messing things up.
If that was my bike I would pay $75.00 and get a brand new 1975 OEM style harness from Parts-N-More. And do not modify it at all. Modify switches but not the harness.
Plug and play.
Parts-N-More is exactly the inferior quality I mentioned. Maybe it's different now, but I ordered one in '06 for a 750 K3, waited a week, opened the box, took a long look, shook my head, retaped said box, sent email, waited two days for a reply, paid return shipping for a refund. I spent fewer days with a soldering iron in my hand with two used harnesses that I did on that debacle.