The Dana 20 was used in CJs from 1972 until 1979. It was introduced in larger Jeep trucks in the 60s, but it wasn't used in any Jeep trucks after 1979. 1972-79 has off-set output shafts. The Model 20 has a lower front output shaft and a upper rear output shaft. All models have single shift levers. All gears are stamped with 18-8-XX.