I put a Runtz on it and it's DOA. Doing some research on the Runtz (of course after I bought and installed one) I discovered they have a high failure rate out of the box. It seems any conversion of the actual gauge would be a challenge. I did, some years ago, own a 55.1 panel that I converted to 12v. It never occurred to me that I might need to protect the gas gauge and I put over 100K on the truck after the conversion with the gas gauge working fine the whole time. Since I now have a much harder time crawling under the dash than I did in 1970 and having read tales of woe from folks who say they've destroyed their gas gauge on 12v, I'm being a bit more cautious about possibly killing mine. I think what I'll do is put a buck converter on the gas gauge, similar to the one I put on the heater motor. They are inexpensive and easy to install. The one on the heater seems to be working great. The one I put on the heater is good up to 10 amps output and the one I ordered for the gas gauge is 2.5 amps which should be more than adequate.
Buck converter
