Master cylinder swap

This is my first posting under the brake section, but here goes. I have a 64 Dart that already has manual disk brakes on it. The master cylinder is leaking out the back and needs to be replaced (front brakes appear to be dragging, too). What master cylinder do I order? I don't know what car it came off of, which is what they usually ask. After I take the mc off, is there a number they can use? Also, what good quality MC should I get as I don't want to be replacing it in a year or two? Thank you in advance.