where did you see a 2.8 litre diesel MB in W123 chassis? there were only 4 incarnations as far as I recall.
200D
220D
240D
300D
there was never a 280D - 280 (petrol) yes, but never a 280 diesel
The W123 cars were not marketed as luxury vehicles, they were more marketed as durable tanks that can be on the road for a very long time and can sustain a lot of torture. The W123 was like an AK47 of cars, easy enough to be rebuilt by illiterate peasants, durable enough to go into the deepest bushes of africa and come out too.
the diesel ones can even survive a nuclear EMF blast, once the diesel starts you can remove all electrics including the battery from it and it will keep on running, unless you pull the stop lever on the pump or twist the key to off.