The Buick XP300 was one of two new dream cars built in 1951, the other being the GM LeSabre. Collaborators on the Buick Y-Job, Harley Earl and Charles Chayne split ways and both built dream cars to compete with each other. Chayne's car was the XP300, while Earl's was the LeSabre.The two cars shared many components that included the supercharged V-8 engines, push-button seats and windows, and power jacks that were operated by the driver. Despite these similarities, the two cars had radically different styling. The XP300 had an almost typical Buick look to it, but it was much wider and longer than the production Buicks at the time.

source: Wikipedia