Update-

Found an easy way to adapt the speedometer.

Go to the parts place and buy a speedo cable from an 86 Mustang GT without Cruise. $17 from advance auto.

Search for the correct speedo gear that you need (Tremecs have a 7 tooth drive gear) here...

http://www.mindspring.com/~steveflyer/speedo_gear_select.htm


Disconnect your cable from the back of the cluster and pull out the flex cable almost all the way out from the sheath.

Locate a fairly straight section of the cable sheath under your car (usually along the frame rail) and cut the sheath removing the part that attaches to the tranny. Remove the flex cable out of the Ford sheath, match up the trimmed end of the Mopar cable and cut it close to the same spot.

Then feed the flex cable back into the mopar sheath and reinstall the cable to the speedo. Install the trimmed section of ford cable & gear into tranny. Don't forget the lock clip and O-ring.

Then snake the cable into the ford cable and try to butt the ends of the mopar and ford sheath together. Ideally you want the flex cable inside to butt inside the speedo gear and cluster before the sheaths touch. If they do, pull the cable out of the ford section and trim more testing again. Once you get about an inch gap. Take a piece of 5/16 fuel line and hose clamps to splice the sheaths together (making sure you sheaths are as close together inside the fuel line before clamping down).

Cheap, simple and very effective.