I was wondering the same thing, and as I've heard it, the rear will work, kinda, but will look weird. It will cover up the flip-down license plate gas filler, and you'll have 2 spots to mount your license plate. I've decided to just suck in the stock bumpers for now.
1973-74 Novas are unloved for no good reason. They have their own unique style that I appreciate. Let's leave 1973-74 Novas alone. I don't mind modifications (like tucking the bumpers) but totally changing the front end because you don't like the looks is just wrong (in my opinion). If you don't like the 1973-74 front end and like the 1968-72 better then don't buy a 1973-74 Nova. Just buy a 1968-72 instead. Sorry, just my opinion. I love all (real) Novas. Even the forgotten and unloved 1973-79 Novas.