Differences in Tachometer Connections
 

I posted this over in Rennlist.

Big difference between new and old Tachometer.

https://rennlist.com/forums/924-931-944-951-968-forum/1398591-need-advice-on-tachometer-944-s2.html#post19287055

I answered you over on the Rennlist thread.

TLDR the tach you ordered is for an 87/88 944 S (16V 2.5L) and it should work - just hook up the three prongs and leave the bulbs and other prongs alone. You could even swap tach faces if you felt so inclined to ensure the redline matches.

Thanks for the input. I installed the updated tachometer into the car and I'm happy to report that it works perfectly!