We first suggest contacting Speedometer Service, out of Milwaukee, WI. They can assist you with adapters, cable gears, and new cables for virtually every application. The phone number to reach them at is: (414) 463-6660.
Speedometer cables may be purchased at your local auto parts store. Auto Meter speedometers come with a standard 5/8" x 18 threaded cable input that requires a .104" sq. male drive. The speedometer is calibrated for a 1:1 drive ratio (1,000 RPM at 60 MPH input at the speedometer head.)
If the vehicle tire size and/or rear end differential are not stock, a different driven gear in the transmission may be required for speedometer accuracy. If a change in the driven gear is made, you very likely will also have to change the drive gear in the transmission to maintain the proper gear tooth arrangement. Another approach is to use a "correcting ratio" drive joint to adjust the speedometer input to 1,000 RPM at 60MPH. The ratio can be determined by comparing your speedometer reading against another car having an accurate speedometer and dividing the same speed (Accurate speed / Your speed = Ratio needed.) Auto parts stores or speedometer specialty shops (see above) carry "correcting ratio" drive joints.
Also, see electronic speedometers throughout our online catalog. These speedometers are programmable and feature push button calibration. They can be calibrated repeatedly with tire and gear changes. Senders are available to convert from mechanical take off or electronic sensor.