I always enjoyed the Team Action cards when I was a kid - I appreciated that they showed team logos and helmets, while the Topps cards from the late 70s had to airbrush them out, or go for the helmetless shots. Since they were not the mainstream sets, I guess, they have never been highly popular, despite showing some beautiful action shots of some of the best players of the time. The 76 set is the exception, since I think they were fairly limited in the first year of production, and the fact that they were stickers caused many of them to get used for the intended purpose!
All of that being said, I think unopened boxes from the 70s are still pretty neat, and look great in the box. The lack of high value individual cards, or a big premium on PSA graded cards would reduce the "lottery" factor and keep them from being very expensive. If I had to venture a guess, I would expect a $3-5 retail price per pack.
I always like reading the Fleer Sticker Project blog, and they have a nice overview of the set here:
http://fleersticker.blogspot.com/200...-football.html
Happy collecting!