I am looking for an aftermarket tach that would be compatiable with DIS on my '95 88. I have located several OEM insturement panels with the factory tach in in but in looking at my FSM, the panel wiring harness is different with the optional tach.
I got lucky enough to find a wiring diagram for my display on my Turbo Grand Prix. There is a white wire that you can use for the tach signal. Pm RobertISaar and see if he can get you a diagram for your car.