If you're adventuresome you might try connecting your 6v gauge as you normally would with a 6v system. I converted my 55.1 panel to 12v years ago and did nothing with the gauges other than change bulbs. It didn't occur to me that I might have an issue. As they say ignorance is bliss. I put over 100K on the truck after the conversion and never had a problem with 6v gauges running on 12v.

Save a life, adopt a senior shelter pet.
The three main causes of blindness: Cataracts, Politics, Religion.
Name your dog Naked so you can walk Naked in the park.