I hope now, you are putting together the new engine. I have never worked on a 240D but I think it must be fun doing it since the engine is small and there should be a lot of room under the hood.
I do not know anything about the 240D but I got a chance to look up my 123 CD service manual today. It seems to me your 240D has the glow plug system just like the late model W123 300D. If that is true, the 4-point connector should be the same. If you have the old glow plug system (wired in series), the diagnostic is different.