Yes, it was a Ford concept. It was designed and built in 1966. It took many of it's ques from the GT40, including fixed plexiglass side windows, flipper gas cap, and grommet-laden bucket seats. The auto show pic I posted was from the January, 1967 Detroit Auto Show at Cobo Hall. The Mach 1 hinted at the beefier styling of the late 60's / early 70's Mustangs, including the production Mach 1.
Ford designers Pete Stacey and Chuck McHose - who also collaborated with Pete Brock at Shelby on their version of the Mustang - penned the Mach I concept. The updated Mach 1 with the Plexiglas headlight covers did the car show circuit in 1968