I don't know if this is too old of a topic, But I too am thinking of doing a ML320 to om606 or om603 swap...
I've done some research on the topic and know the problems I could be getting into trying to put a very long engine into such a small engine bay.
My thought is, if I could get it to fit physically onto the transmission (swapping a 722.6 diesel bellhousing onto the ML's transmission) and mount up with the ML430's driveshafts and trans mount; I could move the rad out of the way (put it on the roof or something) and there would be enough room to put it under the hood..
Any input would be helpful.