according to that picture, you will want to tap into pin number 5 on 101-2.

might want to check out this thread i made a while ago concerning the pin numbers though...
http://www.rdtiburon.com/index.php?showtop...9&hl=pin+number

pictures are gone, but it may help you out if you are having problems with not getting a tach signal.

 

Or if you look at the back of the gauge assy, there is a screw, and it says TACH SIG on it.