Well, Since I bought my 72 the speed-o has been WAY WAY off. It was reading about 80 MPH or more when doing 45MPH ( I was pacing my wife in the van). There were a number of mods done by previous owners, 4:10 Gears and wrong size tires (about 2 inches smaller in diameter). ANy way I put 225/70 R 14 on all around, and I replaced the 4:10s with 3:50s. Now the speed-o is still off reads about 65 MPH when doing 45 MPH. I have an FMX tranny. Does anyone know what speedometer gear I would need to bring this in closer to actual?

Thanks

 

Try this calculator to see what you should be running. You will need to change the speedo gear. Not sure just which one though.
http://www.csgnetwork.com/speedcalc.html