Amp gauge vs volts gauge?

The other gauges, you'll need a 6V source. There used to be individual gauge regulators, I'll have to think of the name

If you have electric wipers and 6V heater blower you can run "volt a drop' resistors from the parts stores. You will need to measure the amps draw of 6V loads because the resistors have to be tapped to match that reading

Most old motors don't care about polarity. Wipers, heater, starter, should all work same, and generally won't hurt a 6V starter to operate it on 12. use a 12V solenoid, tho.

Use a 12V coil and matching resistor just like our 12V Mopars