616 - 2.4L 4 cyl non-turbo (like forever, largely done in 1985)

617 - 3.0L 5 cyl non turbo and turbo versions (thru 1985)
http://en.wikipedia.org/wiki/Mercedes-Benz_OM617_engine

602 - 2.5L 5 cyl turbo
http://en.wikipedia.org/wiki/Mercedes-Benz_OM602_engine

603 - 3.0L 6 cyl turbo (1986/1987) later 3.5's were the "rod benders"
http://en.wikipedia.org/wiki/Mercedes-Benz_OM603

Not sure a 603 will fit in a Ranger but have read about several 617s in lots of non MB rigs. Check out 4btswaps dot com for some intel on Rangers (and others)

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"Opportunity is missed by most people because it is dressed in overalls and looks like work" - Thomas Edison-
1979 300SD
1975 450SL
2014 Ram Cummins Megacab (tow rig)