took ours apart and yup there is another 2 parts as jim showed in his pic. The 2 parts are a combo, a housing Metal piece in a rectangle shape with a foam gasket that fits inside of it. It was stuck to the tailpanel when I took it apart. if you had to, it could be made.
the part in the middle
bill v
69 Firebird Convertible (wifes car since 1979) Goldenrod Yellow, 350, plain Jane Car was stored in garage since 1990
I need help, if anyone see's I'm going down the wrong road--Straighten me out!