Founded in 1967 by a pair of former Mercedes-Benz engineers, the engine builder and independent tuning firm AMG quickly became known for shoehorning large engines into small chassis.

Combining the Teutonic quality of Mercedes-Benz products with a no-holds-barred flair for exotic performance and bold aesthetics, by 1986 the company had flourished into a known brand.

At approximately the same time, AMG started developing racing engines with Mercedes-Benz, and thus began its slow walk toward the marque’s corporate umbrella.

Put simply, AMG had achieved marked, worldwide success by following a simple ethos: If your pockets were deep enough, they would build it for you.

This 560 SEC 6.0 “Wide Body” is an exemplary representative of one of AMG’s wildest and most famous creations.

The cost of its 6.0-liter DOHC engine conversion, and wide-body package from AMG—tacked onto the sticker price of a brand-new, flagship SEC Coupe—made this car one of the most expensive roadgoing marvels of the...