school me on differences between Dart, GT, and GTS?

In 1967, the Dart 270 was available as

* Dart 270 ....... 2-Door Hardtop
* Dart 270 ....... 4-Door Sedan

Usually equipped with;
* 225/145 HP ~ 6-Cylinder
* Torqueflite
* Rocker-Panel Molding
* Upper Body Side Molding
* Trunk-Lid Molding
* 270 Interior Trim
* 7.00 x 13" Tires
* Wheel Covers
* AM Radio
* Rear Speaker
* Cigarette Lighter