If you swap in a 7-tooth drivegear for the tranny tailshaft together with a 21-tooth speedo gear, your speedo will be dead on accurate. With stock diameter tires and 3.73 gears, the speedo gear to drivegear ratio needs to be exactly 3:1 so you could also use a 6-tooth drivegear with an 18-tooth speedo gear. That would be even better 'cause the gear teeth will be thicker and stronger.
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