[Henry's Lady's Man]

FWIW, From what I've read, the wiring back then was cloth. When cloth insulation got wet, it would "bleed" electricity to the body where it made contact. With negative ground, this left corrosion at those spots. With positive ground, it did not leave corrosion. So, in the late 50's, WIRING INSULATION WENT TO THE NEW PLASTICS, AND MADE THE CORROSION A NON-ISSUE... no more "bleed".
The other development was that AT THE SAME TIME, car radios started using diodes which passed electricity only one way, necessitating negative ground (Oh, maybe the electronic engineers could have made diodes pass the OTHER way, but they didn't?).
SO AT THIS POINT, NEGATIVE GROUND worked for radios, and there was no more corrosion issue ('cept at the battery terminal).
Somebody will correct me if I am wrong. Chuck