[Catnip]

What replacement speedometer cable unit do I need to buy (and where) for my 68 XR7 (automatic 302 engine)?

 

[ahunt191]

http://www.cougarpartscatalog.com/c7zz-17260-a.html

 

[Harvey]

The gear changes based upon the ratio of the rear end doesn't it?

 

[ahunt191]

Yes, Driven gear tooth count = Drive gear tooth count * Tire revolutions per mile * rear end ratio / 1000

Here is a very nice online calculator: http://www.cougarpartscatalog.com/speedocalc.html