Replaced wiring harness wires
What I did was to ease the metal connectors inside the wiring harness out from inside it so I could solder new wires to the backs of the metal connectors. I won't do that again unless I have to. It would have been far easier to just cut the cable a few inches down from the connector end and solder new lengths of wires to those. But here they are. This approach does work fine and it actually looks cleaner, but I think I'll value speed and sanity over good looks next time.