While waiting for my boards to show up today, I was reading the front page and saw this project replicating the 74181 in low level gates:

https://hackaday.io/project/25596-mega-one-8-one

I also saw a note that the 74181 is no longer in production which raised a red flag for me.  I'm not sure why, but I never checked this - I always thought it was still in active production.  And so that makes me fail one of my objectives - to use only active production parts.  That's kind of disappointing, and I'm not sure why it never occurred to me.

At some point I may start a new project for another CPU, and I will take this into account.  I really like this CPU design that spins it's own ALU which doubles as the video rendering output:

https://hackaday.io/project/20781-8-bit-color-computer-from-ttl

I will probably have to do something similar.  But I'm not sure what the next CPU project for me will be.  I'll finish this one first.  But I have learned a lot, and I'll know a little better next time what is reasonably available.