Buick needed a car to compete with the Pontiac GTO so the Gran Sport was born. The engine of choice for the GS was the Wildcat 400 which was a little larger and produced more torque than Pontiac’s 389 cubic inch engine. However, the GTO was still a better performer because the GS weighed a little more and the transmission was geared for a smoother ride. Buicks customers were a little more mature and sophisticated and demanded more comfort features than the youth oriented Pontiac had. However, Pontiac would not be king of the hill forever. By 1970 the Gran Sport had grown into a dominate performer. Motor Trend Magazine declared the GSX 455 Stage I the fastest car they had ever tested up to the time.