You can power the guages by putting a self tapping screw into the center link of the battery which will get you 6 volts------------

And/or-----for 6 volt starter--you can use two 6 volt batteries in series for the 12 v system and a lead off of the center to the solenoid for the starter(use a 12 volt solenoid but for just 6 volts to the starter(and/or gusge)