Does anyone know which wire either off of the tach or computer I would use to hook up aftermarket tach (auto meter)? Do I need an adaptor?

 

Hook it up to the first tach signal on the passenger side. If the tach only has red, green, and black wires, then you shouldnt need an adaptor. I installed Auto Meter's digital tach, installed it EXACTLY like the raptor shift light, and set the tach to 4 cyl.... for some reason, that's how it works, since it's not set up to read off a single coil -- but it works perfectly!

 

Do you mean the 1st coil pack toward the front of the car, what color wire?

 

If you can't get it working, Ford Racing has a tach adapter that works very well. That's what I got and it was easy to install. -Joe