If all else fails, I have an instrument cluster for sale.
Mine does not like to reset properly on my OCC. If I push the button a couple times it will go all the way back to "0". I never checked to see if it worked when it did not reset properly. Sometimes the connectors get cruddy, and cleaning them may help.
If its a mechanical odometer then it might be as simple as replacing the gear for it. Check out Performance Transmissions and Parts. A friend of mine just bought a set of gears from them for a relatives 93 Crown Victoria, but they have parts for most mechanical odometers. - Peter