KPH speedometers

Professor Fate said

The problem with just re-decaling the speedo is that while it may read speed in KPH, the odometer is still clicking off "miles"... I would think a more accurate way would be to figure out the % difference between KPH and MPH and regear it at the trans, or use a gear reduction/multiplier on the cable. That way the speedo & odo are both changed the same amount, and the existing numbers can remain on the face. ??

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Difference between kilometers and miles is 1.6 (I mile equals 1.6 kilometers). In order to regear it at the transmission you just have to multiply the tooth count by 1.6. Sounds easy but unfortunately the highest tooth count is 45 afaik. That would mean you can only use this conversion method for very tall rear end gears and/or tall tires (45/1.6 = 28. If you would need a 28 tooth count speedo gear you can instead use 45 tooth gear and it would work in metric mode).