I am putting together a YouTube series on this project. The first video in the in the series is:
There is a playlist that I will fill in as I go here: Z80 Retro! YouTube playlist
The basic plan is to build a Z80 board that only uses through-hole parts so that any beginner can build one. The only problem is that I could not find a through-hole micro-SD card socket. So you have an option of either attaching a SD breakout board from Sparkfun (DEV-13743) or soldering on a surface-mount SD socket.
With a 10-MHZ Z80 and a bit-banged SD card driver, the transfer speed is about 150kbits/sec... which is a single-density 5 1/4 floppy... but with zero rotational delay. So it runs at a traditionally realistic disc-speed.