You could also swap the brains of your old cluster onto the face of the 04 Cobra's. It would keep PATS and your milage the same and just use the faces of the 04 gauges.
On my '02 GT it was easy and you are still plugging the wiring into the same plugs however as mentioned the boost gauge will change things. I swapped an 01 cobra cluster onto my 02 gt, the redline, speedo and tach were off but the cluster still read the same milage.
Forgot about the boost gauge with my first post so that is one thing I don't know how to overcome.
I've seen the write up on mustang evolution. I'm wondering if it will work the same? The 03 cobra has indigo lighting so the wiring might now work. Also, the boost gauge just needs a vacuum line ran to the motor.
I'll ask around I called coastal dyno and they said I'd have to disable the pats system but it still would read the correct mileage. I've heard there's ways around disabling the pats.
I have tested them buy just plugging them into the car. The mileage will be the mileage from the cluster I know that. I am interested in where this goes I want to do the same with my Mach 1
I ended up testing it for the first time. I'd get the pats disabled at coastal dyno down the street but, I'd rather get my 03 cobra mirrors and side scoops painted first.