My '55 Customline was 6-volt positive ground. It had a 272 Y-block with a crossover exhaust pipe that ran in front of the engine. I still laugh just thinking of it.
Our '59 Galaxie is a 292 Y-block. I did overhaul that engine but I switched to an alternator and electric fan so we could run it in parades all day (the Woodward Dream Cruise) at idle speed. It worked out perfectly and I couldn't be happier with the alternator setup. That, the electric windshield wipers and power disk brakes on radial tires are the best retrofits. I will never go back to stock.
Voltage regulators have two long resistors clinched to the back side. They are famous for getting brittle and breaking. If you 'manhandle' them the resistors can break as well. Rarely do the relays go bad. Just exactly WHAT do the resistors do? A regulator compares the battery voltage to the generator voltage. Since the 14-volt generator needs to overcome 12 volts for charging the battery, Ford threw in resistors to make the two 'even' when the battery is full. Otherwise the generator would never stop charging.
Think about this; OEM Voltage Regulators don't care which polarity they are connected to. There are no diodes, but simple relays and two resistors. They can run with positive or negative ground just the same. Most do not say whether they are neg gnd while others do, just to let you think you're buying the right one. The truth is, there is no polarity in a Ford regulator but there is in the generator. That's where your GEN light comes in, to 'tickle' the armature into making a tiny bit of magnetism before it starts turning. - Dave