Any insight to swapping out an M110 for a...?
 

Am giving some very serious considerations to doing a removal of an M110 to make room for an M104...or ? Anyone here done anything like this or know of anyone who has? I'm sure I should also mention that the surgery is intended for a W123 (of course, right?). Any comments should only stick to the topic of swapping something into a W123 and not talk about "just get another car, etc. etc. Please! My preference is for an I6 petrol burner, but...!

I'm considering doing this just to get a working motor back into my 300TD. Offhand, I'm fairly positive the block dimensions of an om603/6 and a m103/4 are the same, and therefore you can use W126 mount arms and spacer plates. Transmission wise, unless you are feeling saucy, I would go with a 722.3/4 out of a W124, I believe most of the important parts are common enough to work with the W123 chassis, though you might need to be creative with the shifter linkage. The two main hiccups I see are engine electronics, which thankfully are decently documented if you want to go aftermarket, and the throttle linkage & TB. I'm not sure how a M110 is actuated, but with the om617a I'll basically have to ditch everything forward of the firewall and get creative, I'm tossing around ideas for TB, but the consensus is a non-ASR unit from ~93-94 with the electronics gutted is the way to go. If you want to go with a M103, some of those headaches go away, but there's a bit more fabrication to put EFI on an M103.

OM.617 will replace the M110 in W123 with few issues. Same mount arms etc

You can even bolt it directly up to the 722.3 that's on the M110 at the moment--although you'll need to do something with the vacuum modulator....

--Probably the vac/auto trans valve fitted to OM.617 pump connected to the vac-mod of the M110 trans, will allow decent operation if set up appropriately....

Defo fits though....

Any thoughts on doing this in the w114? My plan is to put a 240 motor in but any thoughts would help...

The suspension crossmember is the same as the r107 ~ sl 2 seater so you might look at the diesel sl450 rehacks.

Mercedes built 'em...
 

Yes, Mercedes built 'em right off the assembly line, they were w115's. Better known as 200d's, 220d's and yes 240d's. I've been told by Mercedes tech's that the w115's had a great deal more body welds than the W114's though.