That's the "old" OM 603 but a 2.9 liter ??? I have a OM 603.960 and that is a 3.0 liter. There is also a 3.5 liter version but I really don't know about a 2.9.
I'll have to ask an owner. You can see them occasionaly in the streets over here. In Belgium, they made some publicity with their Mercedes engines.
But this "big" motors aren't very popular in Europ : to much taxes!
Danny