The '71-'73 Mach Is used the same rear spoiler as the '69-'70 Mustang. As you can see, there is no shock-absorbing provision on the rear bumper. Car models that were carried over to '74 were redesigned to have energy-absorbing bumpers both front and rear. This shot also shows how small the 14-inch wheels look by more modern standards. With those enormous wheelhouses, a 16- or 17-inch wheel could easily fit and still have good proportions when compared to the overall size of the car.