I'm afraid I can't help with cush drive, but I think master cylinder is simply maitre cylindre. Is the French Rally by any chance Arts et Elegance at Chantilly? If so, I'll see you there with the other Morgan Club de France members.
This is a charity supporting rally based around Draguignan organised by the Lions Club there, called "Retrolions". Sadly forecast is not looking great for Sunday. If it is bucketing with rain at 07.30 when I have to leave to drive to Draguignan for 8 o'clock kick off, I will probably wimp out. My health is rather fragile at present and driving soaked for a day would not improve it.
In the mid 1990's, on holiday in the south of France with the family in my e34 M5 BMW, the clutch master failed. It was peak August holiday season in France and many dealers were closed. When I did get through to an open one, "Maitre Cylindre" did not seem to ring any bells, so I changed my request to "Cylindre Hydraulique de l'Embrayage à la Pedale", which they did understand. I failed to find one and decided to try and drive back to the UK through the night without a clutch, which could be disengaged. I gave up about halfway, as the starter motor was beginning to object to starting the engine in first gear, which on the M5 is quite high. We left the car, with all our luggage at a French BMW dealer in Lons-le-Saunier and took the train back to the UK. To add insult to injury, I was pickpocketed in the metro going from Gare de Lyon to Gard du Nord in Paris. Not one of my better trips.
Wilson