Olds master cylinder help

I need help with a manual brake set up on a 72 disc/drum. I need to know if anyone knows a source for a master cylinder with as rod or at least the clip in the back of the master for the rod. All the Master cylinders I can find have nothing to hold the rod in the back of the master cylinder. Has anyone ever used one of these. I don't know if I trust it with nothing holding it in. Also should a 72 Cutlass with manual disc/drum brakes use a 2 bail equal size reservoir master cylinder. I have also read the prop valve is different with manual or power discs. Is this true?