This is the GTA Kammback. It was a concept car where Pontiac tried to design a Firebird with a station wagon style rear extension. It obviously never saw production but the car does have some fans out there and actually is not a bad looking car with a whole lot of functionality.

This car may have been developed in an effort to take care of the most basic problem with third generation F-Bodies; a lack of space in the back end. A white wagon and red wagon were built (total of two). The white wagon has long since been destroyed in a fire, so this is now a one-of-a-kind and is all factory original with no modifications. Both these cars also featured the Recaro Seat Option, available from 1985 to 1986 (not to be confused with Recaro Edition, from 1982 - 1984).

Gert Hofman of Holland writes: "In 1986 somebody at Pontiac really lost it and designed a station [wagon] model for the Firebird and called it the Kammaback. Pontiac, of course, never produced it."

(source : http://www.indiemonkey.com/firebird/)