Bob Gelsi (long time Mustang restorer in South Jersey) cut this out of a factory dual exhaust car. He thinks its out of a '67 (it was cut out a long time ago). It has the 2 holes for the exhaust bracket, the inside has an additional piece of sheet metal reinforcing. No crush tubes where the dual exhaust bolts go through the frame. I did not mark up the photos to point out the items - the markings would get in the way of all the pieces being referred to.
Anyways, I always thought crush tubes were the norm. But I don't know as much as you guys, so h it is.......
Rob