Email me off list. I have a gauge cluster from a 96 Mystique with tach. Pre 98 have a cable actuated speedometer, after that it's different, so you'd need to get the cable type, and then make sure the wires are there for the tach. IIRC, they are. If you're interested, email me.
jc-aimhigher@webtv.net
Trust me, it took me forever to find a couple, and now I'm down to the last one.
HTH John
