1982 was the year that most of the updates became standard equipment. The 1982 up is a heavier, better built Gleaner rotary. A couple of places to look for one would be Ironsearch.com or fastline.com. These two sites cover a majority of the dealers in the US and Canada. Any Sn above 2501 should be fine and the 83 N7 started with Sn3501. Good luck