Just got back from a 700Km trip with the new 205/70 R14 tires&rims. The "feeling" of the ride and the comfort were radically improved from the 225/65 R15 tires and BBS rims it previously rode on.

The handling is the same at speeds below 140Km/h with the mention that the 205/70 R14 tires puts less stress on the servo system and this shows.

My advice for every 500 Sel, 300 SDL owner would be this: stick with the original tire&wheel combo. Like many other aspects of '80s MB engineering this aspect is perfectly thought and balanced too. Switching to other types of suspension or wheels will surely affect the ride quality in not so pleasant ways.