I am doing my Traction at the moment and I have redrawn the wiring diagram with a 6 volt section to run the fuel gauge, dash lights and wiper motor. The fuel sender is in the same circuit too but this does not really matter, be it 12 or 6 volts.
I have bought a tiny 12 volt to 6 volt converter that I will connect from the 12 volts switched circuit (ignition switch) and then the output will feed an isolated 6 volt circuit feeding the wiper motor (a 6 will not work on 12, well not for very long anyway) and the fuel gauge (as it is difficult to change on the Traction as it is part of the speedo etc).
The starter motor will stay at 6volt though as this should be OK for a while, but I always hear about how they burn out and then the next conversation will be, they will last forever...
The converter I used I got off amazon - type in Vktech converter and a bunch will pop up, I have the smaller 5amp version.
I suppose I could run two 6v batteries in series and take 12v from the pair for lights, starter etc. & 6v from one for all the rest? Would that work...?
I like this approach a lot.