You may be right, Ulf but the hanger is the same on the '66 models without the notch and there is a bumper in the way, although the exhaust may have been attached before the bumper. I prefer to think there was a miscommunication between the engineering and design teams. It would have looked much better tucked up into the notch in the rear valance.
When I had my 1st '65 Dart back in 1966 people would ask me why my exhaust tip hung too low. I asked the dealership and they told me that's the way they all came and it was supposed to hang down like that. I just accepted it but didn't think it looked right then and it still doesn't to me, especially when you look at how nicely the Mustang GT exhaust trumpets of the same era fit through their rear valance.
I guess we'll never know... :)
