it is gonna depend on the fox that you are refering to. no body cares about the 79's, most of them are beaten up drag cars now anyways (why would anyone want a 4cyl Pffff). I think finding a originall fox will be the hardest part. there will be a big market eventually to restore them back to originall. If in the 60's they had the same technology we have now I am sure they would have modified the **** out of theirs also!
SVO's, 84 GT's, 93 Cobra's etc are already getting to that status. the others will take awhile as they made so many.