A shop near me could probably tell you what is the best approach, Bob's Speedometer.com, Howell Michigan. They have been in business a long time and did a quick calibration for me with no charge when I dropped in to talk to them.
1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy
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