That's the '60-'63 setup; the external vacuum diaphragm arrived for '64 (across all Chrysler Corp carburetors, no matter whether made by Carter, Holley, or Bendix). The external diaphragm was adopted because the dirty gasoline at that time tended to gum up the previous pull-off piston, but today's gasoline isn't going to do that anywhere near as much or as fast; just give a Pssht of carburetor cleaner through the slot where the pull-off piston link goes into the carb wall (with the engine running) every once in awhile and you'll be fine. Use 1963 instructions for how to adjust the choke pull-off, if needed. Carburetor operation and repair manuals and links to training movies and carb repair/modification threads are posted
here for free download.