A 1965 Shelby Cobra CSX2461 street car sold for $649,000 during Russo and Steele’s Monterey, Calif., auction last August, making it one of the most expensive cars sold during the three-day event. Built three years after Carroll Shelby first began combining high-performance Ford V-8 engines with British-manufactured Ace-Bristol roadsters courtesy of AC Cars, this particular Cobra benefitted from advancements at both AC Cars and Shelby American Inc., and it represented the quality of engineering work that Shelby was beginning to incorporate into the Ford Mustang.

At Russo and Steele’s upcoming Monterey auction August 18, 19, and 20, a number of equally intriguing cars are prepped for sale, including a 1969 Ford Boss 429 and the first 1970 Chevelle LS6.

During the late 1960s, it was Chrysler’s 426 cu in Hemi V-8 that dominated NASCAR racing. Ford’s rebuttal was the Boss Nine, a 429 cu in V-8 engine, but to meet NASCAR’s homologation requirements, the company had to incorporate that engine into a regular production car. Even though it was Ford’s Torino body style that graced the NASCAR tracks at that time, the company decided to allocate the engine to the Mustang. However, because the traditional Mustang body was too narrow to house the motor, Ford contracted Kar Kraft in nearby Dearborn, Mich. to perform the necessary modifications—alterations that included lowering the suspension and moving it further outside, relocating the battery to the trunk, hand-rolling the fenders, and hand-fabricating the hood to accommodate an oversize air scoop with a manually controlled intake flapper valve.

The finished product earned the distinction of being the most powerful and—at $4,800 per car—the most expensive Mustang ever produced to that point. From January to July 1969, Ford produced only 857 Boss 429 Mustangs, and only 93 were painted Raven Black (as this example is), making black the rarest of the five factory colors that were available. In its prime, this particular car competed primarily in drag races not far from where it was built; and over an 18-month period from 2005 to 2006, it underwent a complete restoration back to its original factory-issued condition.

Also up for sale in Monterey is the first 1970 Chevelle LS6 that Chevrolet ever made. Ordered by a GM executive and built on December 9, 1969, this car boasts two build sheets, one of which is labeled "Pilot job" with a handwritten note declaring, "if it had wings it would fly."

With 450 hp at 5,600 rpm and 500 ft lbs of torque at 3,600 rpm, the LS6 Chevelle represents the pinnacle of GM auto engineering. It also was the only full-production vehicle in history to surpass the Corvette in horsepower rating. In 2010, this particular LS6 received a concours-level restoration at the hands of MuscleCar Restoration and Design in Pleasant Plains, Ill., and since that restoration, the car has logged only one mile of road time.