Autoblog and Yahoo may earn commission from links in this article.Mecum has called it the main attraction of the entire Harrisburg sale, and on Saturday, July 25, we think it will earn such a billing. The car is a 1970 Chevrolet Chevelle SS LS6, a high point of the American horsepower war, finished in Tuxedo Black with white stripes and backed by the kind of documentation that separates a real one from a tribute.The Story: GM Pulls Out All the StopsFor years, GM capped engine size in its midsize cars. By 1970, with emissions rules, insurance surcharges, and efficiency standards all closing in, the company scrapped the rule and dropped the biggest engine that would fit into the Chevelle's bay. The result was the 454-cubic-inch LS6, rated at 450 horsepower and widely believed to make well beyond that. It was the most powerful factory engine of the time and placed the Chevelle SS at the very top of the muscle car market.AdvertisementAdvertisementAlas, Chevrolet dropped the LS6 after a single year, which makes 1970 a one-year-only proposition and this car a snapshot of when the era peaked.MecumView the 3 images of this gallery on the original articleThe Numbers: 450 Horsepower, Backed by PaperThe drivetrain is the one enthusiasts dream about: the 450-hp 454 LS6 paired with a Muncie four-speed manual and a 4.10 Positraction rear. Equipment includes power steering, power brakes, a cowl-induction hood, headrests, and correct five-spoke SS wheels on reproduction Goodyear Polyglas raised-white-letter tires.MecumWhile rarity makes this Chevelle a hot ticket item, its the accompanying documentation that elevates it to top billing. Just 4,475 LS6 engines were built for 1970 across Chevelle and El Camino, with most experts putting the two-door Chevelle count at well under 4,000. This car backs its claim with two original build sheets, including a second copy found tucked under the front seat, and a listing in the LS6 Registry. It was displayed at Carlisle in 2020 for the engine's 50th anniversary.AdvertisementAdvertisementThe car has been repainted once in its factory Tuxedo Black over a black vinyl split-bench interior, and it still wears its original body panels.MecumView the 3 images of this gallery on the original articleThe Market: A Benchmark in a Cooling RoomThe broader muscle market has softened over the past year, but blue-chip, fully documented cars have held firm and in some cases climbed. A registry-listed LS6 with two build sheets is exactly that kind of car, the sort that sets a number rather than chases one. As the headline lot of a 1,200-car sale, it will be one of the clearest reads on where the top of the muscle market sits right now.The TakeawayIf one car defines both the peak of the horsepower war and the value of honest paperwork, it is this one, and it crosses the block Saturday.AdvertisementAdvertisementThis story was originally published by Autoblog on Jul 23, 2026, where it first appeared in the News section. Add Autoblog as a Preferred Source by clicking here.