Rally dash gauge voltage. 5v or 6v nominal?

6 volt or 5volt
Yes!

One thing to look at is the current or wattage draw.

(Just using 100 ohms as a number)

5V/100ohms = 0.05A power = 5W
6V/100ohms = 0.06A power = 6W


The higher the wattage the farther the gauge will move. (The heater coil gets hotter and the bimetal bends more)