My tach was really easy to put in but I did it half-assed. I shoved the signal wire in through the main hole in the firewall with all of the other wires, put one of the little connecters on the pos wire and just shoved it in where the power window fuse should go ( I don't have power windows), shoved the dimmer wire into the back side of the plug going into the headlight switch(top right wire...it works and dims), and found a screw to ground the neg wire. Unfortunatley my ground wire broke (got snagged) and there aren't many good places to ground under the steering wheel. Don't know which one you were looking at, but I have the Sunpro Supertach II (like 2 inches across) and the signal wire was just barely long enough. Good luck if you get one. It's not hard at all.
89 Tempo GL
rust holes = weight reduction