Buick’s Gran Sport models blend upscale trappings with potent performance, making them more refined and unassuming than typical muscle cars of the era. The moniker first appeared as an option package on the 1965 Riviera and Skylark, delivering increased output with beefier V-8 engines. By the 1967 model year, the Gran Sport had evolved into its own line, with the Skylark GS 350 and GS 400 offering more aggressive aesthetics to complement their enhanced performance. In 1970, Buick replaced the GS 400 with the most potent variant yet, the Gran Sport 455, featuring a burly 455-cubic-inch V-8 capable of 350 horsepower and 510 pounds-feet of torque. Available transmissions included a base three-speed manual, Muncie M-21 four-speed manual, and Turbo-Hydramatic 400 three-speed automatic. A Stage 1 option package elevated output to 360 horsepower with a specially tuned four-barrel Quadrajet carburetor, modified cylinder head with larger valves, and a more aggressive camshaft, among other upgrades.

The Buick Gran Sport offered here is understood to be one of only 164 convertibles equipped with both the Stage 1 package and the Turbo-Hydramatic 400 transmission for 1970, according to data compiled by the Buick Performance Club. Build information from the Buick archive at the Sloan Museum in Flint, Michigan, indicates that it was first invoiced to the Cuyahoga, Ohio dealership C.M. Jones, Inc. It came finished in a highly desirable triple-black color scheme—one of only two Stage 1 automatic-equipped convertibles so-delivered, according to owner Michael Leith—and was laden with sought-after features, including power steering, power brakes, power windows, power outside mirror, air conditioning, cruise control, bucket seats, full-length center console, AM/FM radio with eight-track player, rear speaker, tilt-steering wheel, Rallye Ride Control Package, Soft-Ray tinted glass, four-way power seat, door guards, Convenience and Instrument Groups, and Super Sport wheels.

In the late seventies, the Gran Sport was owned in Pompano Beach, Florida, according to a copy of a 1979 title on file. By the 2010s, it had returned to Ohio, where it was acquired by the previous owner in 2013 and shipped to California. There, it underwent a multi-year, rotisserie restoration, completed in 2016. Invoices detailing the extensive work are on file and available for review.

Mr. Leith acquired the Buick in June 2017, ensuring that the car was meticulously maintained and in good repair, as evidenced by its lovely presentation, replete with well-detailed engine bay and undercarriage. With a history file containing Sloan Museum build data confirming it as an authentic Stage 1 Gran Sport Convertible, restoration and service invoices, owner correspondence, and registration documents, this potent and rare, triple-black Buick drop-top will hold immense appeal to the astute muscle-car collector.