If it was only that easy. lol. I have one on mine using the factory dash tach. Im using a converter from dakota digital. SGI-8 with a MSD magnetic pick up so i didnt have to cut into the coil harness.The Dakota digital box was about 90 bucks and the MSD pick up was about 70. Mine seems to be about 100 rpm off at idle and about 1000 rpm off at 6400. Not sure if its the tach or the converter. Autometer makes one but you have to cut all the coil wires. I need to try another tach to see if its the tach or converter.
Clip an MSD GMR Pickup (p/n: 8918) to one of the pink/yellow coil wires to get the signal. Set your tachometer to '2'. If your tachometer doesn't have this setting then you can use a Dakota Digital SGI-8 signal processor to multiply the signal x4.
Here is the reply from autometer.
In order to wire in a tachometer, it will require a #9117 Auto Meter tachometer adapter. This requires re-wiring the power for all 4 coils on one bank. From the factory, you can not cut just one wire to affect all 4 coils, since the injectors use the same powers as the coils, and the coils need to be separated from the injectors.
I have included a write up from a factory application. Keep in mind the color of the power wire is likely different.
Will Need 9117 tachometer adapter. Recommend only experienced technician for this application! Will have to cut brown wire with a white stripe at each of the 8 coils. Wire all 8 coils together going from coil to coil. After all 8 coils are wired together, hook to red/green of the tachometer adapter. Hook the solid red of the adapter to the original power source for the coils. This way all 8 coil draw their power through the tach adapter without interference from any other components.
The write up speaks of cutting the separate power to all 8 coils, but I have found that in many cases you can get away with cutting of just one bank due to Chryslers wasted spark system. Thank you. Cory Tech/Service