well, there are several serial number breaks for parts like oil lines and such on these cars i believe. You probably got the early serial number and needed the late serial number, or vise versa. I went through something very similar with my 79 300CD, and i just ended up going down to my local Parker Hydraulics store and picked up some German DIN fittings and made my own oil cooler lines. Worked out great, and ended up increasing my flow rate and cooling of the oil.

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2003 Dodge Ram 2500 Cummins - Georend fully built trans, Banks Big Hoss Bundle, Smarty Tuner, 5" turbo back exhaust. 500 HP and 1100 ft/lbs to the ground.
1979 Mercedes-Benz 300CD - Lost to a four car pile up on 275, Thank You Michigan Drivers.
1986 Mercedes-Benz 300D - Sold, Euro non-turbo car.