Pontiac built three prototypes of an extended-roof Trans Am Kammback concept ... think 'station wagon.' GM Authority noticed that one of these will be auctioned off by Mecum in January. The particular example up for auction served as a pace car before GM scrapped plans of putting it into production. It kind of looks like the only major change from a stock Firebird would be the removal of the rear glass, and replacement with a fiberglass top to extend the roof line out to the tail lights. Kind of the same way Callaway customizes Corvettes today. See below.