if you got a Zenith tube, they should all be interchangeable, permitting you have the proper yoke. I used to know, but after years of reading things and my job burning me out, it's hard to keep track of what yokes go to which chassis.
I think the U2000 and K7400 are the same yoke, cause they're both standard res. U5000 might have its own shit, which is confusing cause I would think it would be the same as the K7500 cause it runs medium res, but the U5000 and K7500 do not use the same yoke. the K7500 out of my Blitz 99 actually has a label on it that says to replace the chassis with K7500 only, and I'm thinking that exists because of the yoke. also be mindful there were multiple revisions of the K7500, there's a K7501 and a K7502, each using a different yoke. I can't remember if the K7400 shipped that way too.
I don't know 100% for certain, but maybe the K7000, U2000 and K7400 all use the same yoke..?