I've never had one rebuilt but I was thinking about the option before I found my NOS unit. A quick Google gives several results. I know nothing about the quality of their work but here are a couple places:

https://www.bobsspeedometer.com/1/120/services.asp
https://www.bobsspeedometer.com/1/120/services.asp

Follow my Duster 340 restoration progress on FABO http://www.forabodiesonly.com/mopar/showthread.php?t=225784

Kevin