Be very careful about picking a master cylinder and try to keep the same diameter and stroke as the original single line unit. I'd rather have a new-condition original brake system instead of the imaginary advantage of some half-donkey conversion to a poorly engineered dual circuit system. I don't recall hearing about any carnage on the road from total brake failures back when single-line systems were in general use, and dual systems didn't even exist until I was in high school!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!