I've recently finished a project that implemented a mc68000 microcomputer board for a 80s industrial control system. It's a great way to do a deep dive into micro computer design, and the older technology makes it possible for 1 person to have a pretty decent understanding of how the system works. Implementing the programmable timer modules was definitely a challenge to get them cycle accurate.
I really want to adapt what I've done into an amiga500 accelerator board.