Finished soldering LEDs (39) and switches (10 + 2 banks of 8) to the front of the board, and everything seems to work. Added the LiPo connector on the back and it all fits nicely in the case.

I had a bug in the layout. My first version treated all I/O requests (IN and OUT instructions) as coming from the switch bank/to the Program Output LED display. On this version, I decided to get fancy and only use those for I/O on port 0xFF. Unfortunately, I messed up and NAND'd D7-D0 instead of A7-A0. So I didn't solder the 7430 (8-input nand), and instead jumped the output pin (pin 8) to a via carrying A7. As a result, 128 ports (0x00-0x7F) request the switch bank/LED bank on the board; but the other 128 (0x80-0xFF) are available for external use (via the IORQ, RD, WR and address signals in the header).

Next step, I may play with that, and hook up a simple keyboard or something. After that, possibly find some code for BASIC or something (if I decide to dig into CP/M again?!?)