There's very minimal difference in the doors.
The opening around the exterior handle is smaller on the older doors. It varies from truck to truck (probably plant to plant) but around 1995-1996 they enlarged the opening and changed the handle to have a thicker plastic bezel around it.
The older doors also don't have the indentation needed for the 1995-up door module ("inner door skin") to fit properly; you can kind of force it and it still works, or smack a dent where needed with a ball peen hammer.
Biggest potential trouble area though is just that over time the dies they stamp the sheetmetal out with get wear on them, so the bigger the difference in years from door to cab and you're more likely to have fitment problems that no amount of adjusting will solve. You could get lucky and they go right on and fit like champs, or you could have crazy, ridiculous gaps and problems opening/closing no matter how much you jack with it. Been there, done that.
Richard