Engine numbers have never been used to identify model years etc, only frame numbers. There appears to be more engines produced than whole motorcycles. One reason could be that Kawasaki sold engines to other manufacturers to use in three wheelers that proliferated during the early eighties.
I've never seen frame numbers in a finishing sequence , only starting frame numbers for each year.
Although , this writer states the total numbers of KZ/ Z and VN made over the 10 year manufacturing cycle.
www.motorcyclespecs.co.za/model/kawasaki...asaki_z1300%2079.htm