If Patrick Duffy had not returned the Ben Stivers character really would've turned out to be Jock.
Patrick's resurrection from the dead more or less ruined Steve Forrest's chances of remaining on Dallas as a re-cast Jock Ewing.
Even though they tried again in season ten it still didn't work out. In both instances of the character the intention was for him to be Jock. If he wasn't meant to be Jock then why did his X rays match Jock's, when they wrote Steve Forrest off the show the X rays weren't mentioned again. They concentrated on the polygraph test saying that he only passed it because he believed he was Jock. The X rays were conveniently forgotten. Two completely different men can never have identical X rays, it's impossible therefore Wes Parmalee had to have been Jock Ewing all along.