In all the books and and discs that I have I can not find a wiring diagram for a factory gauge set up for a 1967 Impala. All books have the idiot light set up. I have a tach that I would like to install in my car. There are two wires. One looks to be a ground that I have seen from the back of the dash but I don't know where the other should go. Does it go directly to the (neg) coil or is there something that goes in line with it? Since my gas gauge didn't operate properly I have gone to an auto merer gauge that hooks up nicely and reads correctly. The tach fits where the gas gauge was and looks better than something strapped to the steering wheel. Thanks, Paul.