* My personal favorite is the 90ish 350SD, SDL (126.134, 135). Relatively fewer of them made. Better resale (important after you've put thousands in to refurbishing). The most spirited diesel, IMO, of any of the pre-140 diesels. A well set-up 350SD is as close to gasoline performance that you'll find. Of course, if you're just looking for an image, then there are a lot of plodding hacks out there to choose from.
* The MB Club magazine "The Star" did a feature story one month, of someone's restored 350SDL, complete with center fold. You'll need to check their index for which month.

I'd buy a late super cherry 560SEL before a 350SDL. M117's don't blow up and you get to enjoy twice the power and a lot more options.

If you want to own an expensive engine buy the V12, at least you get something for all the effort.

Answer:
 

This is turbo
300SD W140.134 1992-1993 OM603.971

This is turbo
300SDL W126.125 1986-1987 OM603.961 I6

This is turbo
300SD W126.120 1981-1985 OM617.951 I5

This is turbo
300SD W116.120 1978-1980 OM617.950

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This is turbo
300D-T W124.133 1986-1987 OM603.960 OM603.962

This is turbo
300D 2.5 W124.128 1990-1993 OM602.962 I5

This is turbo
300D-T W123.133 1982-1985 OM617.952 I5

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This is turbo
300TDT W124.193 1986-1987 OM603.960 OM603.962

This is turbo
300TD W123.193 1980-1985 OM617.952

Naturally Aspirated
300TD W123.190 1979-1981 OM617.912

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Naturally Aspirated
300D W123.130 1977-1981 OM617.912 I5

Naturally Aspirated
300D W115.114 1975-1976 OM617.910

don't forget the 300CD (turbo) (OM617.952 from 1982-85)

Similar to the 82-85 sedan, but with two doors. Most body and interior parts are harder to find, but forward of the firewall it's identical to the sedan and wagon. A n/a version was made for a few years prior to 82. Relatively rare.

I actually find more n/a 300CD's for sale in my area than the turbo versions.

I know, it's off topic, but do you want a 560SEL? A friend of mine is selling his because he bought himself a V12. I think his asking $3000 and as far as I know the car, it's in decent shape. PM me, I'll give you his phone#.

No thanks I won't be in the market until later next year.