Is there a difference? Don't they both have the same windshield and front side windows? I do not know this for a fact, but I can imagine Ford keeping the costs down by using as much interchangeable components as possible. Perhaps someone else knows?
There isn't a single piece of glass that will interchange between a 71-3 coupe and fastback.
The trim can be identified by the part # molded into it. It'll be something like "D1ZZ-XXXXXXXX". If the first two "x's" are a 63, then its for the sportsroof, "65" for coupe, "76" for convertible. This stand for basically any part made. Most interchangable sheetmetal parts have a 65 number, such as fenders, doors etc.