I have a 63.5 R code with the T-10. The part number for the speedo drive gear (the one on the output shaft) is C2AZ-17285-A. The guy who just rebuilt my T10 said his parts source hadn't seen one in a while and the first place I dredged up on the internet said the same thing. But I did find one at a place call NOS Ford Ltd in Texas. Didn't think to ask if they had more than one.