The '38 speedometer uses standard cable and standard ends, the cable is not terrible long and has a pretty straight shot from trans to speedometer. The cable ends are square drive, and the screw hold down ends seem to be the standard sized that fit just about everything. Someone with a lathe could turn you an adaptor if nothing is available. All speedometer driven gears are plastic. If you know the tooth count of the drive gear in the transmission, the gear ratio of the axle, and tire diameter, you can figure what speedometer driven gear will get you close. Due to the age of the speedometer, it's linear accuracy is likely off. Mine gets farther off the faster you go, so I geared it to be correct at 60mph, anything slow or faster is slightly off.
