Yes they do fit and for the sake of drilling 3 holes in a 3mm sheet of metal dont bother changing the frames.
Remove the old mirrors, line up the 300 mirrors so you know where they are going to mount. Then get some of that white touch up paint, dab some on the bolt holes then put the mirror in its position. the white paint should mark where the holes need to be drilled. You will need to chop the bolts down from what I can remember but I bought some stainless ones and replaced them.
As for the wiring, the plugs are different and the wire colours wont match. I stripped the old mirror and wrote down the wiring then rewired the wires on the motors on the new mirrors to match.
Hook up the heated mirror glass then glue the trim panel back. I didnt use the trim panel mounts but you could modify them I think the plug gets in the way though, cant remember.
I Bought a couple of late Disco 2 folding mirrors for my 200, I wired them up and they are wired differently to the 300s and 200s. I now have them fitted to my 300 ES, I even wired up the ECU and the different mirror switch for them too !
If you have a look at the last 2 pictures here ->
http://members.mud-club.com/profiles/petergalileo/gallery/vvn There you go !
Peter
