Originally Posted by Army

I think I read somewhere that the oil pan design is different and that the W123 OM617s won't fit with ease. I'm not sure about that though...

Oh yes and here's a picture of a non turbo OM617 - see for yourself - does it look the same?



Picture taken from this thread:-

http://www.peachparts.com/shopforum/showthread.php?t=289886

Sounds like you want to bolt on a turbo at a later date - people have done this but there are several differences between the OM617 and OM617a that were incorporated by Mercedes when they did the original modification. If you are going through the effort of doing this job I'd look into making the OM617a fit from the outset.