65 Barracuda rolls when in park

I haven’t spent much time looking into this, but have an issue with my 65 Cuda. 273 2bbl automatic. Trans shifts great, reverse good. Only issue is that it rolls in park. Is this an easy fix. Any help will be appreciated.
Only guessing here, but it has 2 shift cables, one is for park. Either needs adjustment or its broken.
I have the same transmission, but its in the spare parts pile.