The 70 Swinger tips are 14" overall in length. The bracket is located 3-7/8" in from the exit end of the tip with a stand of 1". These are designed for applications with lower rear valances.
68-69 Dart ,70 and up Duster, Demon and Sport models were equipped with the longer 17" overall tip. The bracket on these are 7-3/4" in from the exit end of the tip with a stand of 1".
Here you can find some pictures that might help.
http://www.accurateltd.com/A-body-Tips_c_116.html