By 1972 the muscle car era was ending in slow motion, and Buick’s Gran Sport had already been demoted from a standalone model back to an option package on the Skylark. This survivor still wears its factory paint, original interior, factory vinyl top, and a numbers-matching 350 four-barrel. Here is what actually changed in 1972, why the horsepower ratings dropped so sharply, and why an unmolested GS from this exact year is so hard to find.