The forward piece of duct and the opening in the case changed at some year model along the way. The vents can be moved from one to the other. I took the chrome vents off of a 67 assembly and put the black plastic vents from a 75 model on it. The chrome vents are just too much in my eye. Most of them are pitted and/or broken today anyway. Polishing that much chrome detail could take a week.LOL One option you might consider is having the plastic vents vacuum plated. It would have to be clear coated to stay on there. Have fun and keep up the good work