For your 94 Ranger, you can change the speedometer gear at the transmission. To calculate which gear you need, all you have to know is the percent error and the tooth count of the gear that is in there now.
If your speedo is reading a known percentage high now, you will need that percentage more teeth on the speedometer gear to slow it down.
More info on the calculation and the gear part numbers in the Speedometer Correction section of the Tech Library at www.therangerstation.com
If you still have the old transmission, just pull the gear out where the speedometer cable entered and swap it into the replacement trans. If not, you should be able to order the gear. Be sure to specify that it is for a manual. Speedo gears for automatic transmission are different.