I bet they are different but I don't know for sure...the reason I say that is , look at the Chevelle vs El Camino.
El Camino is based off of the chevelle wagon..same car really..There is even a cover you can take off to reveal what would be the rear floor of the wagon. the camino has sedan doors and the windshield is different so I would think that means the "cab"( if you want to call it that) is not the same shape as the hard top. jmo(guess)
I base those comments on the 1967 model because I have owned two of them ...I don't know about the rest of the years.