Your missing the plate steel mounting bracket (mounting bracket and side cover all in one). It is shaped kind of like the State of Texas with a slight bend in the middle and 4-holes in it. Two holes are used to screw the selector switch to the plate and two are used to mount it to the transmission using longer top cover bolts.
Hopefully you have this funny looking piece in your junk parts box and just didn't know what it was...
Mike B
