Autometer suggests that I use their 9117 tach adapter to get a tach signal.I am wondering if i can just use the stock tach signal? the one going into my stock tach, and if so what wire is that?

 

Your mustang has whats called double fire spark.
3 coils, 6 cylinders.
Each coil fires 2 cylinders at a time. One thats under
compression with a fuel load and one thats expelling
exhaust gasses.

The OEM tach works off the HIGH SPEED CAN BUSS.
Unless you can intercept and decode the CAN BUSS
and get the tach info out of the data stream, its tach
adapter for you. Set it on 3 cylinders for correct display
of RPMs.

You mentioned the dash tach and tapping into that signal?
Whats wrong with the OEM dash tach you now have?

 

just got off the phone with the autometer folks and they said exactly what you did haha, so it is adapter for me, and cause i wanted a shift light, and i love the raw look of a dash tach

now its time to hit up ebay

 

Thanks for checking the accuracy of my information.
That makes me feel all fuzzy and warm inside.

Sumpin like thisums?

 

haha i was on the phone before you posted trust me if i would have seen your post i would not have even called

and yea sorta except i spent 4 hours last night with a saw, lighter, mallet, and drill and steel, and fabbed my own bracket so i dont have to drill into my dash in a place where if i decide to back out i dont have to look at some giant wholes in my dash, i will post pics!!

 

I dont see any big holes in the dash in the above pic.
Those are Roush vent pods...