Headliner Question

71 should also be a bow type. They changed to the hardboard sometime in 72. A 72 could have either type depending on the build date.
I dont see why you couldnt throw an ABS one in a early car. The ends tuck under the glass seal and the sides are held in by trim. Most of the headliner weight is supported by the dome light, sunvisors and rear view mirror.
I can say this, if you have a bow type now thats what I would stay with. Its much better looking in my opinion.