Little known fact.
That was a prototype of Chevrolet's attempt to rival the styling success of Ford's Thunderbird. It was to be called the Bel Aire "Stubby", named after GM Chief Alfred P. Sloan's son, who was nicknamed "stubby" because he was short, fat, and just generally "not right".
... or so the story goes.
With styling like that, I can't believe it never got off the ground.
One of the great oddities in American car industry lore.