The 2017 Mustang Shelby GT350 (Ford). THERE’S a monster Mustang on the loose in Michigan. A prototype of what’s purported to be the 2018 Ford Mustang Shelby GT500 has been spotted on the streets outside the automaker’s Dearborn Development Center. In video posted by fan forumMustang6G, the super ‘Stang calmly, but not quietly prowls the perimeter of...