Converting '68 120 mph Rallye Speedo to 150 mph

60 on the 120 is in the same place as the 75 reading on a 150.

How exactly is the odometer going to be correct. The same number of revolutions is going to give an entirely different MPH reading on each speedo. Are they changing the odometer gearing?



The change the magnetic something or another in there and it works out correctly.