Does it make any sense at all to buy the less expensive gas MB's
and drop in diesel engines from donor cars ?

I see wrecked diesel's for low dollars, and their gas powered counterparts
(same body) for low dollars.

It is a straight swap. You need to make sure you have to correct mounts for the center of the engine. You will also need little things like heater hose, power steering pipes. It will be straighforward if you have a doner car.

Totally straightforward if the donor has the same chassis and wheelbase as the gasser and you use the full driveline. I MIGHT run into trouble with my 190e diesel, as I want to use the 190e tranny and driveshaft with the 190d engine. If the back plate on the diesel doesn't want to fall in exactly the same spot as the 16v, I'll have to do some fabricating at the front motor mounts.

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'79 300SD W116
'86 190E 2.3-16V W201
'92 300D 2.5 W124
'99 E320 4MATIC S210

In December, I replaced a low comp. M110 with a reconditioned OM617 (loop GPs) in a '81 280E.
I had to deal with the A/Cond compressor on other side of engine, electrical connections for the temp sender being on the other side of the engine and the fact that the 300D PO had removed the GP relay and used a push button for the GPs.
I needed to repair the Tranny oil pan as the PO had the OM617 overhauled, but they idd not locate the tranny dipstich into the inlet manifols and bolt up there, so the oil pan had a fatigue fracture. An easy repair, especially when the PO had been quoted $1400 to repair the tranny!! That was also the reason he sold it to me
I just do not know why he trusts that mechanic (still)

If you have both cars, and they share the same body model, there should be few issues to deal with.

This took me 7 days in amongst other issues. I have a small tool kit and only needed to borrow the engine crane for the job.

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Tony from West Oz.
Fatmobile 3 84 300D 295kkm Silver grey/Blue int. 2 tank WVO - Recipient of TurboDesel engine.
Josephine '82 300D 390kkm White/Palamino int.
Elizabeth '81 280E, sporting a '79 300D engine.
Lucille '87 W124 300D non-turbo 6 cylinder OM603, Pearl Grey with light grey interior


Various parts cars including 280E, 230C & 300D in various states of disassembly.

Before you start, check with your DMV to see what's necessary to run the car on the road after the swap. Possibilities range from nothing needed to a new title needed, at least in my experience in transplanting engines, and there may be more severe restrictions in your own state.