I've designed a Z180 CPU card for the Z50Bus. This has a Z8S180 CPU running at 18.432 MHz, 512k FLASH, 512k RAM, two serial ports, an SPI interface for a micro SD card, and runs RomWBW software (which includes CP/M). The card can be used on its own as a single board computer or plugged into a Z50Bus backplane for expansion.
This is an open-source design so the PCB Gerber files, schematics, and software are all freely available. Details here:
https://smallcomputercentral.wordpress.com/sc140-z180-sbc-z50bus-card/
Another design nearing completion is a combined real time clock and I2C bus master card. I think I will revise the board design to add another I2C socket so the release will likely be delayed a few weeks.
I am planning other designs for Z50Bus.
Steve