I called MB NA today about coolant. The customer service guy there looked up their coolant recomendation. He said they are strict about advising MB coolant if it gets in contact with any aluminum. He said my '82 300D has some Al. For older engines like my '72 450SL there is no Al so they don't enforce the MB coolant only advisory. He could not/would not advise another brand but said it should be supplemented with an anti corrosion additive.
1982 300D Turbo