You will have to cut and have new flaired ends on you pipes. The long branch are longer (who would have thought). Not a hard job but one that you might want to take to an exhaust shop. Other than that you don't need to do anything with your exhaust. Don't forgot about the oil filter adapter. You'll need one of those also unless you are running a remote oil filter already.
Restoring a 1968 400 4spd, numbers matching Firebird Coupe, Verdoro Green. Larry My old 68. Wish I had her back.