Never done it so I hate to give advise. I have done the 240D switch back and forth both directions. I always worried about the fact that the crankshaft is a different number for the manual versus standard. We were able to do the conversions with no NOTICABLE problems.
The differences between shafts could have only to do with the area where the pilot bearing or torque convertor ride, but these engines are balanced with the flywheel included. The size/weight of the two (auto vrs manual) are massively different. It worries me that the balancing of a 5 cylinder could be so different that it would massively throw the thing out of balance. In other words: two different 4 cyl enegines are basically in the same state of balance, very different than a 5 cyl. You will of course need to use the mechanical transmission flywheel, which will be the 4 cyl.
I would think you should see how much the Euro 5 cyl flywheel would cost.
Bosch Master, ASE Master, L1
33 years MB technician