Re: voltage gauge
If you are using a single gauge, you would come off the load side of your isolating switch, if you have an Isolating switch which isolates the individual batteries, you would come off the common of the switch. The gauge when read and the Isolator switch in the #1 battery position will read the voltage of #1 battery, with the switch in the #2 battery position you will read #2 battery voltage. with the position in the #1 & #2 position, you will read the overall voltage, thus reducing the need for a dual volt gauge.
Hope this helps.
Alternatively, if you don't have an isolating switch, which I would find surprising, go off the run side of your ignition switch. In the Chrysler's case it would be the blue wire, but I would be surprised if you couldn't isolate your motor from your battery and therefore what I said previous would apply (isolator switch).
