The early 1970s were a golden era for American muscle cars—a time when massive V8 engines and quarter-mile glory ruled the road. When gearheads gather to argue about the kings of that era, the Chevrolet Chevelle SS 454 LS6 almost always gets the crown. With 450 raging horsepower and 500 lb-ft of twist, it was the bare-knuckle brawler that became an immortal pop-culture icon. But...