Carazy suggestion, but it looks like that 1 piece plastic is 4 legs bolted to the tunnel part of the car. Can't you use four 1/4" washers to lift the whole assembly, or maybe even make a big plate to stick under the whole unit?
Just some thoughts.
*Edit - after looking at the pics a second time, it looks like the unit is riveted to the car. So maybe you can make a round plate to stick in that hole where the whole shifter unit slides down into that one piece unit. Then use the longer bolts to put that factory top plate on top. The shifter unit will stick up top, but if you dremel out the big hole in the plate that was shipped with the shifter, you may be able to make it work.
I'm tired so I hope that made sense.