Buick GSX brochure (edited), 1970. A high performance version of the Skylark, the GSX was powered by a 7.4 litre V8. It was available in either Apollo White or Saturn Yellow. Of 687 GSX models built, 488 were ordered with the 360hp Stage 1 upgrade, costing $113. Motor Trend named the GSX Stage 1 “the quickest American production car we had ever tested."