The air-sprung 300SEL 4.5 is far rarer than the 6.3 (cited as roughly 2,533 built against 6,526 6.3s, and it uniquely paired the air suspension with the newer torque-converter three-speed automatic). Long dismissed relative to the 6.3, the very best 300SEL 4.5s are now recognized as nearly as desirable, and even six-cylinder W108s have posted surprisingly strong results.
300SEL 4.5 rarity versus the 6.3, and the six's recognition catching up
Mercedes-Benz 250S-300SEL 6.3 (W108/W109) · history