A couple of Ford drawings on 1965 Mustang dual exhaust systems primarily for 289 HP engines. Unfortunately, I can't find a drawing on the Arvanode System. These two drawing are from "The 289 High Performance Mustang" by Tony Gregory, pgs 75 and 76.
A non GT "K" code (all three body styles) will have different exhaust tips (non-trumpet style, identified on the drawing as "Muffler Outlet Pipe - 5255") commonly called "downward style tip" and they will not go thru the rear valence.
See "1st Generation 1964 1/2-73 - Questions and General Discussion", the "1966 Mustang" Section for 1966 installation, and the "1967 Mustang" Section for 1967 installation.
I remember a discussion that many "day one" Mustangs got the exhaust mount doubler plate installed behind the rear seat, but that was a while back and I don't remember the conclusion.
Jim
