I have a copy (down in the garage, somewhere) of Serling's second draft of POTA (December '64, if memory serves). The plot is roughly the same -- the ending is there -- though the apes are technologically advanced. Now I don't know how many more drafts he wrote before it was taken from him and Wilson did the final drafts, but honestly, guys, Serling's lead character Thomas (Taylor, in the film) is a fairly long-winded fellow. As much as I admire Serling, his characters could whinge on and on at times. His version of the famous "Take your stinking paws off me..." is something like: "Let me go! Get back! Don't touch me, I say!" I don't recall any monologues or dialogue of any nature that survived this draft, untouched, to the final film.
Again, I don't know how much he changed before Wilson took over. So having this draft and Wilson's final (which is on the web, I think) doesn't tell me what went on in between, or who wrote what.
Sir Rhosis