You have the source for the wiring harness so I won't talk to that. A friend of mine who is very detailed (not a car guy, but a wires guy) replaced every wire in my 62 a few years back. Did an awesome job! There is no question in my mine that what made this all work so well was his "bench" work. On the work bench he tagged/labeled every wire in the harness. EVERY wire! Long before he attacked the car and pulled out the old wires. Once this was done the only challenge was the tight area under the dash to get this stuff in. But with the labels, we never got lost! Just some advice!
Hal