[old gm blues]

I think I can give you a better solution.I took a voltmeter out of a 77 gmc and seperated it from the faceplate.Then I installed it upside down on the original faceplate of my 72 jimmy.I then re-install the needle on the gauge so that 12 volts reads dead center.It took me all of about 1/2 hour.I just ran a + 12v wire from the fuse box to one of the two terminals on the back of the gauge.It looks completly original but gives me a better idea of my charging/battery status with h/p alt.