Modern CRT in 1960s 23" set

[dano]

Please don't flame me for asking this - I plan to make this the livingroom set and it will get a lot of use. I do plan to eventually restore the set at some point in the future.

I have a 1969 (or so) Zenith color console with a 23" picture tube. I would like to install a modern chassis/crt in the cabinet and I'm concerned about finding something that will line up with the mask and mount properly. As I mentioned, this will be our main TV where it will see a lot of use, and I would like to preserve the stock chassis/tube. I would also like to have a composite input. I've started looking at craigslist and it seems like 25" is a common size. I measured my set and it looks as though the full 23" is viewable, I suspect that a newer set would have less than the full advertised size viewable, is that a safe assumption? Has anyone attempted to mate a newer CRT to a mask from this era? Are there any makes or sizes that work better, or that should be avoided? Has anyone encountered a modern set that mates up to the 23" tube mask nicely? I would hoping to hear from someone else who's tried this before I start buying used TVs for trial-and-error fitment.