Many people restoring old cars use a dropping resistor to use a 12v charging system and keep their old 6v gauges. Thats what you can use.
-Ken V.
1998.5 SE Praire Tan Zetec ATX
psycho_bass@hotmail.com
Roush springs Roush rear sway bar BAT struts 17" Millie Miglia HT3 and a ton of subtle asthetic mods