David........As you don't give a brand name (Vintage, Beck, Etc.) I,ll give you a couple of things to look for........The brake system is probably VW in origin.......You didn't say if it was a front or rear cylinder.......If the front axle has ball joints, then use a cylinder from '66-67 (wide 5) or 68-77 (4 lug), type 1....If the front has link pins, '49 (I think) to 65............If the rear is swing axle, there are two cylinders, '58-64 for older trannys....and '65-68 units.......If your car has a 12 volt system, you probably have the '65-68 tranny............None of this applies if some one has replaced the originals with an after market braking system.......Simplest thing to do is take the old cylinder to a NAPA store and have it matched up.....You may be tempted to rebuild your part,....Its ALWAYS been cheaper for me to replace with a NEW unit....Good Luck...
