1970 was a great year for the Chevelle. The Coke-bottle styling became more prominent, the roofline was shared with the Buick Skylark, and the interior was redesigned in the name of comfort. That year, Chevy also rolled out a new option in conjunction with the Z15 equipment group, which unlocked more suck-squeeze-bang-blow from the big-block 454.

As opposed to the hydraulic-lifter LS5 that flexes 360 horsepower, the solid-lifter LS6 rocks 450 horsepower thanks to a Holley four-barrel carburetor and an aluminum intake manifold. Four-bolt mains, forged aluminum for the connecting rods, forged steel for the crankshaft, a higher compression ratio, deep-groove pulleys for the accessory drive, and an air injection reactor pump also need to be mentioned, along with a higher redline of 6,500 revolutions.

The biggest rival of the Mopar 426 HEMI further sweetens the deal with colossal torque to the tune of 500 pound-feet (678 Nm) at a lofty 3,600 rpm. Capable of blitzing the quarter-mile in 13.7 seconds, the Chevelle in this configuration is often described as the magnum opus of the muscle-car era.

Very few LS6 454 cars were produced, and finding a period-correct one is nigh on impossible. But unicorns exist, and you’re actually looking at one.

Chassis number 136370B135992 comes from RK Motors Charlotte, a dealer specialized in blue-chip collectibles. In addition to numbers-matching everything, this example of the breed is one-of-three LS6 cars listed in the International LS6 Registry in Gobi Beige and the only LS6 car finished in Gobi Beige and Medium Saddle. Restored from the ground up with original parts, the fully-documented ‘Velle is offered with 14-inch Super Sport wheels, the factory build sheet, and a Delco eight-track player.

Strictly authentic in every respect, the muscled-up coupe rolls on Firestone Wide Oval meats. Sold new for $4,844 by a Baltimore-based dealership, the car shows 76,055 miles (122,400 kilometers) on the odometer and no rust whatsoever. As for the asking price, well, $149,900 is a small price to pay for such a rare machine that will only go up in value.