To me they look like the cars GM had worked up for 1959 before some of the stylists caught a glimpse of the 57 Chrysler prototypes.
proposed 1959 gm - Search Images
The Super Coupe engine has the same basic block and heads as the Mustang V6. You would have to fab up an intake plenum and accessory drive for a Mustang install.
There was a resin kit by an outfit called SMP24. They made 50 of them. I managed to get one about a year ago. Most money I have ever paid for a kit but it is very nice.