Unless you wanted an all original truck it wouldn't matter. As long as whatever front end it has is the one you like who cares.. Mine is a 69 and I have a 68 frontend for it. I talked to a guy who did a 70 into a 68 front end. He got tired of telling everyone that it was a 70 but changed the front sheet metal to a 68
and having to answer all kinds of questions, how hard was it, etc, etc.... Now he tells everyone it is just a 68, saves explaining to everyone
With the current market for these trucks and the customizing that a lot of people do, I really do not think that it will make a difference if it is a 72 prostreet, or a 72 prostreet with a 68 front end on it.
Mike