The fender ext are the same from 71-72 chevelle and elky. Granted that chevelle-elky exts are different but they are same from 71-72. All you need to do is swap out the turn signal bezels and lamps.
You also need a different grille, also forgot in the prior reply you need a different headlight bezel as well.
So in order to make a 72 chevelle into a 71 chevelle you need the following.
1: turnsignal bezels
2: turnsignal lamps
4: headlight bezels
Those four items is what makes the 71 and 72 different, everything else is the same.
Brian, the hood does stick out more on the 72 because the 71 has that raised bar(chrome piece) right below it, where the 72 is flat.