Aftermarket Tach: HOW?

1996 Mustang 3.8L.  How do you hook up an aftermarket tachometer to this wire harnes.  The wire that goes to the cluster (tach wire) does not seen to drive my aftermarket tack?  Help please.  Greg in Texas..

Distributorless ignition would/should need a tach adapter..
 
http://store.summitracing.com/partdetail.asp?part=ATM-9117