You have to use the entire front clip, fenders, hood, grille, bumper, lower valance to make it work. 75 fenders are like 67-69 fenders and don't have the separate fender extensions.
I just re-read my post and realized I didn't type out everything I was thinking. I'm looking at buying a 75 that already has the 72 front clip and hood, and while I like the look (sort of like a 72 Demon), I wasn't sure what parts would need to change. Thanks for pointing it out! So it would take a bit of work and more than a few parts to go back to a 75 sport body front. Gotcha.