Hi, I just purchased a great 200k mile 1980 300D, with the turbocharged engine of a later year swapped with the original engine. I have a long way to go to understand everything about this car, and i've been trying to find a service manual other than a Haynes, or some scammy websites to no avail.
What do you guys recommend for understanding and identifying the mechanical principles behind the various parts of these cars!? Most of the literature posted is directed at fixing problems, but ideally, i'd like to be able to get ahead of things breaking!

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