Not hoping to sound like a wise guy but the best "Made in the USA" gauges out there might be the ones put in your truck originally. 12v won't bother the fuel gauge...if you want a voltage reducer that would be an okay thing if your truck has never been run on 12v. But please get an adjustable one if you do. There will be a period of time where your fuel gauge adjusts from 6v to 12v. As mentioned above once it adjusts to 12v you won't be able to go back to 6v. Please contact me if you need more information.
Moving on with the gauges, the ammeter won't care about voltage and your temp and oil pressure gauges were mechanical. I haven't made any for the 55 but I did post free printable gauge faces for the earlier trucks in the "Interiors" section as a sticky.
