I'm going to suggest abandoning the idea of Mafac cantilevers and going with a nice modern reproduction. Yes, the basic shape of the brake arm is the same, but Mafac cantilevers are the one brake I've never been able to quite down. I guess I don't have Sixty Fiver's level of Cantilever-fu. There are dozens of brakes out there that are easier to adjust and provide just as much mud clearance, and stopping power.