From 1988 the 407 series replaced the 421 series. 789 units in 3 model variants were produced up to 1993. A further 3 model variants were planned but not produced, as the new-generation 408 was presented from 1993. Starting with the 407 series, the Unimog model designations were changed. Even numbers in the sales designation now denoted implement carriers and tractor units with short wheelbases, for example U600. Designations with the number 50 denoted long wheelbases, for example U650. Up to 200 this model designation system was used for all subsequent Unimog model series.