In 1953 Chrysler-Imperial brand switched over to 12 volt. No other Chrysler products switched. Info is from an old shop manual certainly not my memory.
I don't any info about your question if the gauges used a voltage controller or not.
If you have already used 12 volts to test the gauges, my initial guess is your probably OK. The internal gauge workings would have fried right away if they were rated at 6 volt.
I would recommend that you test the gauges at 6 volts to see how they work. If they work OK then go with 6 volt controller.
Or if you can find an archived parts book from that year to see if they used a voltage controller.