Andy, you didn't look in the trunk... I always carry a good 6 volt generator, voltage regulator, coil and solenoid in my 6 volt negative ground vehicles... You know what they say, any extra parts you bring along, you won't be needing.
I did a ground up restoration so I had to completely rewire it. Went 12V neg ground and never looked back. Can get anything I need from any parts store and can use any accessory I want with no hassle. If you are going "concourse" 6V will work fine. If it is a driver 12V has the edge.