The plate looks about right. I think we will need to glue it on and maybe epoxy or "filler" to fill the edges and sand down.
The center square will need to be "centered" in the cutout to estimate the milled look.
As Dave said, After the selector switch is out, we will need to reattach to something. An easy way may be to cut off the screw hole boss from the selector switch and use it with epoxy putty to bond the hole to the frame and fill the voids?
Once cured, the area can be sanded flat and the plate applied.
I think the movie hero looks painted. A semi-gloss black prob will be best and then scuff as desired,. ; )