Bob and Erika Perrye picked up this Saturn Yellow 1970 Buick GSX convertible just this past May, and it’s rarer than the specs alone suggest – Buick built the GSX as a mid-year special for only a few months, with just 678 hardtops total and convertibles rarer still. The 455 Stage 1 engine was so conservatively rated that real output likely topped 420 horsepower. Here’s why this quiet muscle car outran a lot of louder names.