49 has a different door handle ( a pull) and 50-51 (have a push button) and are the same. The hinges are the same on 49-51, though.
Not only are the door handles different on the the '49......so are the locks and latches. That is not to say you can't refit the door with '50/'51 locking mechanisms...but they are not he same and will not work as is. Ray