One-of-one 1967 Shelby G.T. 500 Super Snake remains the most expensive Mustang sold at auction 1967 Shelby G.T. 500 Super Snake. Images courtesy Mecum Auctions. In 2013, a one-of-one built 1967 Shelby G.T. 500 Super Snake, powered by a 427-cu.in. V-8 liberated from Shelby’s Ford GT40 Mk II pro...