Nothing would be gained by having two master cylinders. You would still have the hydraulic clutch setup which leaves a lot to be desired. And it would be a lot of work. You could probably get a master cylinder for the clutch from a truck with a hydraulic clutch with air brakes and then a later brake master cylinder and mount them somewhere on the firewall and somehow hook up linkage. The simplest thing would be to fix what you have and be done with it.