TOPIC:

Hi all!!! A few quick questions about seats:
Anyone know if the KZ1300 1980 seat fits on a 1981?
What about a 1980 KZ1000 seat onto a 1981 KZ1300?
Anyone have a Corbin seat on theirs? If so, which model? (they only have a seat pan for a KZ1000 and it looks like it *could* fit...)
I've tried looking this up everywhere and had no luck, so I figured I'd ask the braintrust in this group   

I have OEM 79 and 81 seats and can look if it would help you...

And this is why I abuse the www.partzilla.com site.
Look up the seat part # for your model and then check the other compatible models.
Part # 53001-1358 is the part # for the seat of the 1980 KZ1300 - A2 and is compatible with the 1979, 1980, 1981 and the 1982 models A1- A4

Link to CatalogKawasakiMotorcycle1980KZ1300-A2SEAT/SEAT COVER

Absolutely!!! Without partzilla, doing a full engine rebuild would be impossible (instead of a massive puzzle to find all the parts across multiple websites )
I hadn't actually thought to look there for the 1980 compatibility, so thanks for the reminder  
That said, partzilla only lists which same part numbers were on which models, but doesn't tell you compatibility. As far as I can tell (looking at pictures and back of the envelope guesstimate measures from photos), it seems that the KZ1000s have the same mounting system with the 2 hinges and sort of loop clasp as the KZ1300, but I can't actually find anyone who's tried to swap them. 
Ultimately, I'd like to get a Corbin seat but I need to make sure their KZ1000 seat pan will work with the 1300 because they won't take back a seat that they don't guarantee fit for (which they don't in this case). I could always show up at the factory to try the seat and get it fitted, but 1000 miles to find out it doesn't seems a bit far  

I wonder if it would be worth asking on the KZ riders forum.  You never know, there might be somebody living near you with a KZ1000 who would let you compare seats.

Have you considered communicating with Corbin and asking if you were to send them your seat, if they could refit with their Comfort Foam and custom one off seat cover?
I know with Katzkin when I first got my 2022 Ford Maverick, I asked if they had templated the seat covers for the Maverick and at that point they had not but did plan on doing it soon and it was only a time thing since it was a brand new model. In the meantime, they suggested that I could have one of their installing companies custom make a set of covers for a slightly increased cost (they suggested that it might be $200 more than what it would be if they had seat cover templates.) You have to realize that both Corbin and Katzkin have one off materials and stitching options available so you are really getting a one off product when you order. When you order a seat, they pull out the templates and the materials and sew it up.
About 15 years ago, I bought a Porsche 928 and the interior was beyond repair. The seat covers available at the time would have cost $12,000 US to redo the interior. I couldn't afford that so I went out and bought a walking foot sewing machine for $600  and 6 European cowhides for $2300 and had at it. Now by trade I was a millwright and pattern making and welding up was in my skills, so doing this work was similar only the material was now leather and the "welding" was now with a sewing machine. When talking to upholsterers after finishing the seats, they were impressed with the outcome because the seat covers were complicated. Time and patience.