So I'm in season 10 and the guy who comes and is Jock's imposter says he is Jock Ewing and they put reconstructive surgery on his skin and body... they find out is not Jock Ewing however they don't say who he was.

Was he a patient nearby who heard the real Jock talk about his family when Jock Ewing was sick????

They really left it up to the viewer as to whether Wes was Jock Ewing or not. The evidence that Bobby found in SA, I thought was weak. The guy was supposedly in SA with Jock and learned all of Jock's secrets while Jock was sick and delirious. He then was in the same helicopter crash that Jock was in. IMO he was Jock but the show was never going to replace Jim Davis. Maybe if Steve Forrest would have stayed on the show a better explanation could have been had.

Somehow Wes gained Jock's memory. They never really explained how he surived the plane crash but Jock didnt.