1965 Dodge Dart Speedometer

13, 15, 12....it all depends on the overall diameter/height of the tire in question. 50 series 16 could be the same height as a 75 series 13...the speedo was calibrated to the OEM tire height of the model via its plastic gear. Its (very) roughly the tooth count /10 for the rear end ratio you are running...ie. a 27 tooth speedo gear is pretty close to a 2.76 rear, 39=3.91, etc. 'just a junkyard find formula but it works pretty good even when looking at the OEM part numbers. you may be able to get a universal style that uses a pickup off a driveshaft or something.

FYI, it's a double screw on ferule, not a later bayonet mount. and you can get the square end cables and cut them to length so all you really need is the correct housing. I pull them from any early A I find, and that has only been 3 as that seems the first thing to go.