[Gary Tosel]

I have two 6 volt batteries in my 36 Ford 5W Coupe that does what you are describing. It starts on 12 volts to the starter only and all other circuits are 6 volts.

This allows charging the batteries in parallel at 6 volts and that was the only change. There is a way to use two 6 volt solenoids to do the same thing as the use of a Orpin switch. I bought the switch a long time ago at J.C. Whitney, but it probably is available on line. It also includes wiring diagrams for use with Ford 6 volt systems that use a ground type starter button.