Having acquired three 240Ds and a Euro 5-speed 300TD in the past four years, I'll chime in -

First try to find one with no, or at least very minimal rust. Could be a tall order if you're on the East Coast or Rustbelt.

My first diesel, 'Miss Diesel', was the PO's teenager's ride for several years. It was a rusty, tired, automatic '82 240D that was ready for the crusher, but I got it cheap and fixed it enough to make it a decent driver. While it's still pretty slow, especialy on hills, it's perfect for local errands. It will get up to speed for occaisional short hops on the freeway, but it's pretty noisy at speed. It does have power windows and a manual 'non-crank' sunroof.

My second diesel, 'Beirut Taxi', was an even more rusty '81 240D 'parts-car'. A basic, manual-shift & windows model that I originally intended as a donor for converting Miss Diesel to a stickshift.
But Beirut Taxi ran & drove so well that I didn't have the heart to gut her. So I fixed her up, patched the floors, and enjoyed her for two years until I sold her to a neighbor.

My third diesel, the 'Wunder-Wagon' is what some may consider the ultimate W123 - a Euro '84 300TD with factory 5-speed, manual windows, manual heat-AC, 60-40 rear seat with three headrests, and third-row cargo seat. It certainly performs better and gets better highway mileage than a 240D, though the ride is much stiffer than the sedans.
Like most old east-coast cars, it has some rust, but not nearly as bad as my first pair of 240Ds.

My last diesel is 'Ol Blue', a stickshift '82 240D with power-windows and Bundt-wheels. Pefect inteior. Good floors, sills and wheel-arches. Only a handful of very minimal, dime & quarter-size rust spots. This car is the most solid, quiet 240D I've ever had. When revved, the engine is quiet too - sounds more like a gasser than a diesel. And it's peppier than my first two 240Ds. Of course, I spent more for purchase, and to fix several mechanical 'deferred maintenance' issues, than my first 240Ds.

All that said, and based on performance, ride and fuel mileage, my 'dream' W123 choice would be a Euro, non-turbo 300D with manual-shift (preferably a five-speed), manual windows and manual heat-AC - also a tall order in the US.
Or, if you're an advanced DIY with alot of free time, you could get a US 300D and convert it to Euro-spec.

For a simple, reliable, gadget-free diesel, best bet is to find a solid, good-running, basic stickshift 240D, perhaps with some minor mechanical & cosmetic flaws to offset a high price. It's usually easier & cheaper for most DIY to deal with mechanical faults, than to properly restore a badly rusted body.


Happy Motoring, Mark

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DrDKW