what year of seat will work?

i have a 79 kz400 and it has the king and queen seat i want to replace it with the flat style of seat,what years will work on this switch? heres the bike below (fairing and luggage on back are gone now

Need a better pic of a side view of the bike.


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heres the side view

This may be more work than you want to do, but I recently had the same dilemma with my seat on my 750 twin and what I did was removed the old cover and all the foam from the seat pan. I then took an angle grinder and cut the edge of the stock seat pan down to where it matched up with the frame and rear cowl. I then bought 1 inch of super high density foam, 1 inch of high density foam, and 1 inch of super soft foam and cut them to the size of the seat pan and used spray adhesive to mold them to the seat pan. My buddy had an aftermarket flat seat cover for his triumph that he wasn't using, so we used it to wrap the seat pan. This got rid of the big seat and lined me seat up perfectly with my cowl so that it would not overlap like it did before. Here's a before and after picture. Don't mind the hideous paint, that's on next week's agenda.