This is one of the most entertaining threads in a long time. I had to run out to the garage in the rain to see if I had something special out there, and I do!
Here is what you are looking at. From the view you took your pictures, the mounting bolts are not visible. Its just a plain old Hurst mounting plate on a 833 4 speed. Good stuff but not unique. I took a few pictures.
Its ok to make a mistake and be wrong for 20 something years. Its happened to many of us. A factory 340 4 speed Duster is still cool.