From Spirit of Speed show vendors:
Resin Porsche 917LH kit. Martini Racing livery
MPC Ford EXP Kit
MPC C3 Corvette "Open Roadster" kit
Minichamps 1/43 McLaren M8B
Resin "Cobra" wheels
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.