New replacement gauge cluster lenses are not available for first gen (94-98) Mustangs. However, replacement lenses ARE available for the second gen (99-04) cars. The lens "looks" identical, and the mounting holes are the same, but my research says that the "difference/change" lies with the "Odometer Reset Button" being different. I'm not sure, but I believe in the 99-04 lens the reset button is longer and sticks out further on the back.
A website that sells replacement lenses call Carbon Driven states that the 99-04 lens can be used on a 94-98 car, but mentions this: Ford factory oem 1999-2004 XR3Z-10890-AA will fit Mustangs from 1996-1998 with minor modification to trip odometer pin on your dash gauge cluster.
However, they do not go into detail as to what "modification" needs to be done.
I was wondering if anyone on this site has done the modification and could share/explain what is involved?