The crimp terminals are one part of the equation, but don't forget that you need exactly the right crimp tool and dies for the job, and the right extraction and insertion tools for the various plastic connector Housings. Pliers won't get it done.

The copper will have almost exactly the same resistance as it did 50 years ago and will not contribute to the voltage drop you have mentioned, so unless the insulation has deteriorated you will achieve exactly nothing by replacing it.
What is worth doing is examining all the terminal attachment crimps (although they are normally fine) and more importantly the mating faces of the connectors. They are almost all tin plated and can usually be cleaned with contact cleaner or a very mild rub with scotchbrite.

One of the main sources of electrical trouble in HKTG is the firewall connector, closely followed by the accumulated wiring alterations by various artisans and ignoramuses during the cars history.
Pay particular attention to the dash cluster earths, the main engine earth, and the main body earth on the left hand inner fender attachment bolt.

Edited by user Tuesday, 12 November 2019 10:37:15 AM(UTC)  | Reason: Not specified