About The 1977 Mustang
The fourth year of the Mustang II did not show great changes. It was very difficult to tell a ’74 or ’75 Mustang II from the ’76 or ’77 Mustangs because they all looked so much alike. However, 1977 did provide plenty of options to tailor the vehicle to one’s personal style and set it apart a bit from past years’ models.
In fact, one of the biggest marketing campaigns for the 1977 Mustang II was the addition of T-tops. This really made the difference in a 1977 Mustang II and set it apart from previous models. However, even the T-tops could not save the Mustang II and bring it out of the sales slump. Even with the addition of T tops the sales for 1977 dropped by approximately 18%. Only 153,117 Mustang IIs were produced that year.
Source: Mustang Forums