How to use 12v negative gnd gauges in a 6-volt positive gnd car

[Eaglescout2457]

Good evening, I have a 1953 Mercury Monterey with an 8BA flathead that is 6-volt positive ground. I understand that the gauges that come factory are not completely reliable and am looking to add aftermarket gauges to my car. I have looked for older style gauges and have stumbled across the Stewart Warner Green Line series gauges. Unfortunately, these only come in 12v negative ground. I am looking to add 2 temp gauges (one for each head), A Tachometer, and am deciding whether I would like an Oil pressure Gauge or Amp Gauge. (I am running a Power Gen alternator with a max output of 60 amps). Is there a way to convert these gauges to work with my car? Photos to show how awesome the gauges look. any help would be awesome, Thank you!