The M Pump is rare on W123s because it was only available on european cars. However, it doesn't offer and advantages that I know of. I just put a european 617 engine in my 300CD and it honestly isn't anything spectacular, other than is lacks all the emissions stuff. From what I've read the motor itself is off higher compression, taking advantage of Europe's higher-cetane rated diesel (can't confirm). Performance-wise I can't really say...

Show me.
 

A 617 with 380 ponies? Even the C111 only mustered 230 hp.

http://www.classicdriver.com/uk/magazine/3200.asp?id=11583

The Fins work magic with the 60x engines, but an iron five pot?

Jay

the non-turbo engine is identical to the american version other than the injection system and emissions. the euro turbo engine is the same minus the EGR.

the m-pump has different elenents inside than the mw pump does. myna does not touch the mw, only the m pump. bottom line, mo' powahh, but mo' money.

The green wagon had that. With the M pump there are stock upgrades that you can do. With the MW pump there are aftermarket elements that you can upgrade with. The MW is considered technically superior, they tend to last longer and are easier to calibrate.