I wouldn't waste a minute worrying about the hatch swap. IMHO those vents on the early cars were unsightly and more trouble than help (read rust magnet). Nissan must have agreed since they removed them on subsequent years. Lose the bondo and the rust and get a clean straight hatch. If, at sometime in the future, you need the one or two CFM those ugly vents provided crack the window a 1/4". You'll be much happier in the long run.
Wow, that was pretty "in your face"! Lone, you must be rubbing off on me.