Saw this on Facebook. Post said Pontiac made these for a dealer in Texas. Poster says Pontiac also installed the "Mustang" emblems but I highly doubt it. I suspect They built the cars to dealer spec and the dealer swapped out the emblems.
Interesting car nonetheless.
From the post:
1960 Pontiac MUSTANG, built at the Arlington assembly plant for the Van Winkle Pontiac dealership in Dallas, Texas.
Titled and badged as a Mustang at the plant, there were between 350 and 500 of these cars built for Van Winkle, all two door bubbletops with the 389 cu. in. big block engine, factory AC, power steering, power brakes and eight lug wheels.