The XP-788, existed as the sole full-scale clay model purportedly crafted for its development initiative.

During the mid-1962 period, GM's Design Center initiated the XP-788 project, prompted by a directive from senior Pontiac executives desiring a vehicle akin to the Corvette for Pontiac's production line. Under the stewardship of Bill Mitchell, the project team undertook their tasks clandestinely within an undisclosed studio dubbed the "Warehouse Studio," situated inconspicuously within a storage facility at the southernmost extremity of the Technical Center. This covert workspace was specifically established to accommodate such endeavors. Regrettably, Pontiac's endeavors to persuade GM management of the viability of a Corvette-inspired sports car were ultimately unsuccessful.