After working on getting the tach to work properly for 3 hours and talking with Tincup, and a phone call to dakota digital, it finally works. Here's the parts that you will need, assuming that you are using a wiring harness from hotwire, bouchillon, or s&p.
MSD GMR Pickup (part# 8918)
and Dakota Digital SGI-8 Tach Signal Interface
Set your tach to 4 cyl
set the dakota digital to 2cyl and the dip switches as follows, 1 and 2 on, 3 and 4 off, the green light will flash 2 times to indicate it's set at 2 cyl. Hope this will help and dont forget to wire it first,lol!