I just realized that I needed to provide some more information on this question. The 3 terminal at the bottom of the tach are G, +, and -. The red/blue wire is hooked into +. There is a black wire leaving G. There are 2 black wires leaving -. One goes up to the clock and the other is clipped. The clock has two terminals: one has the a black wire coming up from the - terminal on the tach. The other wire is a clipped white one.

Does it work this way?: red/white (+) needs 12v power from fuse block terminal #13, black (G) goes to ground along with the white from clock, and clipped black on (-) can tie into the red/white wire behind the instrument panel. ??????

And I still can't figure out how to remove the dial glass......