At one time, it was believed that commercial vehicles would have fewer grounding and corrosion problems with a positive ground system. That's not very likely, but it represents the engineering theories of 60+ years ago. If you decide to switch the ground polarity, swap the wires on the coil primary so the + lead is connected to the ignition switch, and the - terminal goes to the points. Also, re-polarize the generator by momentarily touching a jumper wire from the Battery terminal to the Armature terminal at the regulator. The regulator is supposedly polarity-sensitive, but I've seen a lot of them work OK on reversed polarity. It's possible to buy aftermarket regulators that are designed to work either way, but try the original one first. If it was my vehicle, I'd leave it original, and just mark everything so it's obvious what the ground polarity is.
Jerry
