Well, in fact there aren't too many on the road!... only about 3,000 were made in the 126 body. Mine is running strong and true so far (knock on wood) but I'm keeping an eye on the fuel quality. These are the highest compression diesel engines Benz has ever put in a car (22.3:1) and would be subjected to some awful stresses with low-cetane rated fuel. I notice mine clatters like crazy (at idle and just above) with ordinary garbage diesel, but with a good verifiable premium diesel it just purrs. My 78 doesn't care what you put in it.
Take care,
Dennis