In the late Sixties, Buick elevated the Gran Sport from an option package on the Skylark into its own model, following the trail blazed by Pontiac with the GTO and Oldsmobile’s 442.
With General Motors dropping its in-house 400 cubic inch displacement cap in midsize cars for the 1970 model year, the motor in the Buick GS swole up to 455 cubes, putting out 350bhp and a whopping 510 ft/lbs of torque. If that wasn't enough, you could opt for the "Stage 1" option package that added a bunch of performance modifications, yet mysteriously added only a claimed 10 horsepower bump.
Insurance companies might have been fooled by the 360bhp rating, but the timing lights weren't. Even Motor Trend managed to crank off mid-13 second E.T.'s from their Stage 1 test car, putting it in rarefied company back then*.
This super clean Diplomat Blue 1970 convertible lacks the Stage 1 package, but I wouldn't kick it out of the garage for leaking oil.
*It's easy to forget, given the rose-tinted glasses through which Boomers and us GenX'ers viewed the Muscle Car era during the automotive dark ages of the late '70s and early '80s, that even during its absolute heyday in '68-'71, the number of cars that would run a quarter in the 13s in stock trim off the showroom floor could be counted in most years without pulling off both socks.
You could get big motors in the Mustang-Camaro-'Cuda pony cars, but they tended to be traction-limited; nose-heavy and not enough rubber and weight to get the power to the ground. Conversely, the full-size cars were generally too heavy, no matter what monster mill lurked under the hood. Other than the hairiest Corvettes, only a handful of big-motored midsize cars in any given year could lay down an honest sub-14 second run in factory form.
