1971 Mercedes Benz 300 SEL 6.3, 1978 Mercedes Benz 6.9 & 1992 Mercedes Benz 500E

It's a formula as old as the musclecar itself: Stick a big engine in a car smaller than it was intended for, and the result goes faster. The first Pontiac GTO. The Shelby Cobra. A skateboard with a motorcycle engine. You know the deal.

If any company has the recipe nailed these days, it's Mercedes-Benz. Drive a 493-horsepower SL55 AMG and you'll understand. Drive the twin-turbo V-12-powered CL65 AMG, which ripples out 738 pound-feet of torque, and you'll really understand. Even the pint-size SLK55 AMG roadster boasts a 355-horse, 5.4-liter V-8; it looks like a kitty but roars like the MGM lion. If the bits are mixed right, the handling, braking, appearance, lux factor, and exclusivity get sexed up to match the dragstrip prowess.

Everyone's gotten used to Mercedes offering an AMG version of nearly every platform it makes. But the practice of big V-8 power hiding in a conservative German four-door predates the company's purchase of previously independent performance tuner and race team Aufrecht Melcher Grossaspach in 1999. The first example was the 300SEL 6.3.

Remember the old W109 chassis Benz? Staid. Upright. Boring to look at, if nice to drive. The workaday 250/280/300 S/SE/SEL versions were powered by Mercedes's sturdy inline-sixes. The semi-rare 3.5s and 4.5s got V-8s, sized to match the labels. But 6526 long-wheelbase (SEL) W109s, built between late 1967 and the end of the 1972 model run, were injected with the M100-series 6.3-liter SOHC V-8 borrowed from the engine compartment of the 600 limo.

It wasn't so much the 300 gross horsepower that impressed; it was the 434 pound-feet of torque that got the car moving. A four-speed automatic transmission with a gated floor shifter was the only transmission choice. Another important techno touch was an air-suspension system. High-pressure airbags replaced conventional steel springs, the goal being improved ride quality. The rears leveled the car when it was loaded heavily or towing a trailer. Larger vented discs, beefier high-speed rolling stock, and a structurally stiffened chassis also were among the mechanical upgrades.

As the 6.3 was the company's top mainstream offering (the low-volume 600 fills a spot that today is occupied by Maybach), it benefited from every upgrade Mercedes could muster. Leather-trimmed seats were standard, and genuine burled walnut covered the dash, A-pillars, and several other interior surfaces. Power windows and vacuum-operated door locks, a Behr A/C unit, and Webasto sunroof were standard.