No. The headlight buckets are part of the 71 fenders. In 74 the headlight buckets are part of the header panel. You would need 71 fenders or you have to add 71 headlight buckets to your 74 fenders.
In other words. Yes if you replace a bunch of parts, or no, not without replacing a bunch of parts.
As said above on 72-74 the entire front header panel, grille surround and headlamp bucket area is a 1 piece fiberglass part.
On the 70 everything is metal and separate parts.
I have seen this done quite a few times and IMO if you are going to do it you need to both ends (grille and taillights) or it looks incorrect. Its a lot of work and to be honest if you have a nice 73, you could probably sell it and get a 70/71 (albeit probably a much less nice car).
From my prospective the 72-74 cars are slowing coming into their own, values are increasing and we are now seeing people actually choosing them specifically (mainly due to some experience early in life). The Coda's are less of an issue as the grille is not as radical a departure from the breed as compared to the Challenger, however I really believe that the 72-74 Challengers are unique unto themselves and are just as good looking as the 70/71.
Converting a 72 up to a 70 or 71 is possible but in the end you still have what you started with and the ascetic of the front and back end is not worth the expense or time to do it, but each to his own.
It's not that difficult once you've got all the parts, but make sure you keep the '74 stuff around and painted to match. You're definitely going to want it come sale time. People wanting a '71 ain't going to buy a '74, and those of us who prefer the '72-'74 cars (we exist) will simply view the earlier grille as a liability.