Back to my brakes.......we are trying to order a new master cylinder online. It was discovered after bleeding the brakes and a chuck of debris came out revealing a leak in the master cylinder. My boyfriends suggestion was a dual reservoir master cylinder enabling the back brakes to continue to work if the front brakes go out. I do know the rear brake drums are not what came with the car, they appear to be 10” brake drums, possibly what came with the rear end that was put in from the 70s possibly. Will the original master cylinder work with the two different brake drums? Can a new dual chamber master cylinder be installed, if so are there compatible years or make/models that may work with our situation? Bearing in mind a future upgrade to front disc brakes.

Thanks in advance!!