The M189 is a radical motor with almost 200hp, but they have issues.

I turned down a 1965 300 twenty years ago because my tech told me that the were a bear to work on, and it should be a coupe or cabrio if you are going to have those kind of headaches. I bought a '71 300SEL instead, but I always missed how well balanced the six cylinder car was. Even with air suspension, imho, the v8 W109 cars feel nose heavy to me in comparison.