78-83 Ford Fairmont Wagon.
For all practical purposes, it was the same thing as a Mustang Wagon for these years.
http://upload.wikimedia.org/wikipedia/en/thumb/8/8a/Ford_Fairmont_wagon.jpg/250px-Ford_Fairmont_wagon.jpg
Holy crap, you're right. I owned a '79 Fairmont sedan once. What a complete piece of you-know-what. The '83 Mustang I had wasn't much better, but looked slightly hipper.