Below are Documents and Articles that reference the Notchback option for the 1988 GTA.

Source: Pontiac Date: 11/22/1993 Contributed by Joe Bush
Source: Pontiac Date: 12/1987 Contributed by GTA Source Page
Source: Pontiac Date: 8/1988 Contributed by GTA Source Page
Source: Pontiac Date: 03/02/1989
Source: Motor Trend Magazine Date: 7/1988
Source: High Performance Pontiac Date: 3/2006
Source: Motor Trend Date: 2/1987
Source: High Performance Pontiac Date: 09/2008
Source: Plastics World Date: 01/1988 Contributed by GTA Source Page