Push button 904 Park Shifter Cable

I have a 1963 Dodge Dart wagon with the 904 push button. The park cable was broken so I have a replacement and have it installed in the trans but to install the new one at the back of the push button mechanism I have to remove the old one from a 'clamp' or Park cable Collar as per the pic. Any advice as to how to pry this open without damaging or breaking it? Its sort of hard to reach under the dash but would prefer to do this without pulling the whole set up out. Thanks!
park-cable-lock-dash-buttons.jpg