Can't say on that old of a unit but from 07 and up on the crown vics and taurus' it has become a common problem. The instrument cluster on these is a one piece item, all on a printed circuit that fails. In my fleet of 300, I have had to replace 6 clusters in the past 5 months. I can only get them from Ford and the only way they are sold is by vin number and Ford has to program the current odo reading into the new unit. You can use a scanner to get the mileage reading if it can't be seen. On your rig, you might try checking the wiring connector at the instrument cluster, I have seen a few that the pins came loose