I think '68 used a folded metal stamped clip - been a LONG time since I was in a '68 Barracuda door.
But that's what my '68 Road Runners have had.
Those rods are kinda beefy, have a hole that goes over a rounded peg or stud and the clip goes over the top of the rod.
Later As like my Dusters used smaller-diameter rods & plastic clips.
You might try Dante's, Classic Industries, etc.