I think this was posted here because of the question on Retrocomputing Stackexchange: “What was the last commercial Z80-based computer sold?” (https://retrocomputing.stackexchange.com/a/31883/11579)
https://en.wikipedia.org/wiki/S1_MP3_player used a Z80 SoC, and at least from a quick search, appears that they're still in production.
I love that this site has an Easter egg if left idle long enough.
How much room is there for a custom PCB? I'm a 6502 guy so I would like to keep the case but put something there with my favorite CPU.
I've learned Z80 and 8051 a decade or two ago, and then forgot everything. Honestly both were easy to pick up, but I assume you're opinionated and/or an expert?
Anything in particular that you like about the 6502?
I think people like the way the 6502 wires up to peripherals. Myself I think the Z80 is much better because it has enough registers and addressing modes that you can write compilers for it. I know they had C compilers for it in 1984 because I typed in a C program for CP/M from Byte magazine and got it to run on my 6809-based TRS-80 Color Computer. Programming languages for the 6502 were usually implemented with virtual machine techniques like
https://en.wikipedia.org/wiki/SWEET16
or the truly atrocious
https://en.wikipedia.org/wiki/UCSD_Pascal
which was one reason a generation of programmers hated PASCAL with a passion and declared you could pry BASIC from our cold dead hands.
Myself I'd want to hollow it out and put something based on
https://en.wikipedia.org/wiki/Zilog_eZ80
because it is way faster, has a bigger address space, and has wider registers so you can do pointer math over that bigger address space unlike this turkey
https://en.wikipedia.org/wiki/WDC_65C816
A lot of people enjoyed writing assembly for the 6502 back in the day though.