Smartin, I've not chimed in from San Diego for a while, although I do keep tabs on your magnificent project from time to time.
For what it's worth... free advice... If you have the opportunity to replace the wiring with new, I'd strongly encourage you to consider that option.
Here's why: Plastic wiring is water proof... but it is porous and over the decades, becomes hard and brittle, and more porous. Herein lies the problem, because moisture does get to the copper conductor and it corrodes it over time. Ever notice that really old wire is tarnished when you do strip it? Braided or twisted wire is ever worse. So what? Well, the physics of electricity is that the current flows on the outside of the metal conductor and the corrosion raises the resistance in path of the electricity. That's one reason old cars have dim lights in spite of solid clean connections at the terminals. It's also a prime reason that high amperage leads like battery cables and starter cables are frequent problems. Resistance cuts current flow and raises temperature, degrading the insulation, allowing more corrosion... repeat cycle to failure.
I know personally the best $165 spent on my old Skylark was the new rear body harness. I've also spent a lot of time in really old Navy airplanes with really old wiring (sniff... sniff... "Hey, you smell something burning?"). With a Buick, you could hitch home, but it'd be a sad day.