Our 1956 'Rover 60' two liter sidevalve had positive-earth electricals. I seem to remember some guys in my office saying that positive-grounding increased the rate at which the car body rusted?
Actually, we can thank Ben Franklin for this glorious way of confusing the ignorami. [ IMO People who fold paper shouldn't be playing with electricity anyway ].
Ben denoted +/- for direct currents decades before the likes of Ampere started electrocuting frogs in the name of science, but as he had no way of knowing which way the electrons flowed, he had to guess.