Here is an Ebay auction for an NOS C5ZZ 2A635 E rear parking brake cable by Ebay member "touchmeimsick1" with a starting bid of $150.00:
One N.O.S. Genuine Ford rear brake cable that will either side for the 1964 1/2 and 1965 Ford Mustang with the 289 C.I. V-8 engine.
The Ford part number is C5ZZ-2A635-E. 1964 1/2 65 NOS Mustang & 1965 Shelby Rear Parking Brake Cable Assembly Oem. Condition is New.
Look at the pictures to determine condition for your self. Has been in the box for 55 years.