68' Dart Brake - Remove Master Cylinder

Many of these master cylinders have nothing more than a tiny sheet metal finger/keeper holding the piston and return spring assembly in the bore. So pulling it apart under at the car will often defeat that keeper and pull it all apart ( as shown above ) spilling fluid everywhere. Its all about how old and hard the rubber collar inside is versus how weak that keeper is.
I take master cylinder with rod attached to the workbench and block the piston in the bore before pulling on the rod so it comes apart where I want. In most cases I have reused that rubber collar too. I recall only 1 that stayed in the piston then picked out in pieces. Replaced it with a little piece of hose cut to size.