Look for a gray lead under your dash. Since you don't have a tach now, it shouldn't be connected to anything. This is your tach input. You would also need a ground and 12V supply (normally connected to the purple wire on your switch).
No wires under the dash, but I followed the wiring harness into the shift control and found a gray wire that is not hooked to anything. Just to clarify, I am not installing a tach in the dash, It is a hand held test tach with red and black clip on leads.
That is your tach input. If you want to use it at the motor, it connects to a yellow/gray wire on the terminal strip. This yellow/gray wire comes from the stator and also goes to the rectifier.
Attached the tach to the gray wire. This tach is meant for 6 and 8 cyl. Supposed to double the reading for 3 and 6 cyl. I wanted to check the timing but found the gauge doesn't read high enough.
What I did notice is that the needle was jumping around alot. Like one cylinder was firing intermittently. I tried to adjust the carbs at idle, but that didn't seem to change it.
