There are two different types of carbs on the KZ400's, and I think certain '77 models had the newer design...All are made by Keihin- same as the Hondas of the era, however not really "the same".
But the older ones are 36mm, and use an aluminum piston as opposed to the rubber diaphragms. It also uses a single main jet (of a pretty large size, like 140-150 range) Then you have the newer 32mm's- they go back in time, so to speak by using the Honda-style diaphragm (rubber). They also use a primary and secondary main jet system.
Anyhow, I have a '75 with the old carbs on it. They are about as easy to get parts for as a '37 Bugatti. Just finding the stock jets is hard enough, optional sizes...good luck. There is not much adjustment you can get out of them either.
I lack experience with the later model carbs, but I think the jet sizes are CLOSER to the old Hondas. I also think they are easier to get rebuild kits and jets for, but don't quote me. My favorite thing to do is to go on bikebandit.com, or similar parts fiche site, and look up the parts for each machine in question to see if they interchange.
So on a final note- yes, please expect it to be hard to tune these things in for pods and pipes. Might it be easy? Yes.
But then again, you may never be able to get it to run right. That's why so many guys switch to a single carb setup or a set of Mikuni carbs on these bikes- it doesn't necessarily make it easier, but it's much more feasable because you have an array of jets etc. available to you...