That plastic plug screams 68. Like I stated before 67 has a long screw through that hole that shows its chrome phillips head.. 68 has the screw hidden inside.
In 67 they used a fancy steel clip on a rectangular opening where the arm rest bolts on.
In 68 that hardware disappeared and a simple lag thread screw went into the door metal.
That means the door(s) are definatley 67 model but they have 68 model wing window parts.