The big question is the rear sump. Passenger car 60x's and 10x's have a front sump. You might need the oil pump and sump from a 250D. The 104 mount arms should attach to the block but I don't know how they'll line up with the crossmember. The 124 and 210 which accept 4-, 5- and 6-cylinder 60x engines have the engine and transmission interface at different locations, moving aft with more cylinders. You'll either have to shift the transmission forward and get a longer prop shaft or shift the engine aft. Maybe both as sump clearance allows.

The 60x and 10x have the same bell housing bolt pattern so that should be okay. If your car has a 722.5 5-speed AT, I don't know if the module that shifts from third to fourth needs something from the ECU/EDS. Otherwise it might shift from third to fifth by default. Either way, the 3.46(4AT), 3.69(5AT) or 3.92(MT) diff ratio of the early S280 is way short for a 603 but might be just right for a 602. If you have a later S280 with 722.6, good luck making it shift out of second.

Does the IP use mechanical or electronic throttle? Mechanical is on the block side of the IP.

That looks like a variaton of the Barluk(sp?) rotary vane pump found in late '97-up E300s. I"m not aware of problems with this pump. It has a simple slot drive so failure will probably be more in line with how a water pump fails rather than how the reciprocating pump in 603s fails. Kaboom! It amount to the same thing losing brakes in a 2-ton car

My Euro is rusty but IIRC the 2.9l is a 602, not 601. It's basically the G290 engine. Not sure if it was used in the 124 or 210. I think it was the 4-valve 605 used in the 210 E290. In fact the 2.9 is the 5-cylinder version of the 3.5 but I don't know if the 2.9 has the rod bending propensity of the 3.5.

Sixto
87 300D