Is it possible to convert? Vitesse says unfortunately not. There isn’t the space for the external cylinder and one of the external cylinder mounting lugs is shaved off to make the gbx fit in the tunnel.
There are at least two M3W's about with the external clutch slave cylinder, one belonging to a German owner and the other to someone in the UK that I have seen but cannot remember where. I suspect that if MMC went to the bother of listing them in the parts book there are some more?