Most people are concerned with mating OM61X engines to the existing Land Rover drive train. See for example

Converting a Series Land Rover to Mercedes 617 diesel

Mercedes diesel

I doubt very much if there would be "enough front" in front of a transfer case to fit a 717.41X gearbox and an OM60X engine.

I can probably find engine lengths and gearbox lengths if you need them.

If I were you I'd be looking at W124 4Matic manual transmissions (common{ish} on 260e W124s over here in Northern Europe) and adapting Land Rover drive shafts to fit. This would work for a road vehicle. If you want off road capabilities as well then there's always a strange thing called a "G-wagon" => these things rust faster than Defenders!

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!