Well, another "I've just got the chips" project :-(
However, I have also collated a lot of data, including the Byte Trump Card Article and a couple of books about the Z8000. One by Lance Leventhal, one by Bradly K. Fawcett.
I have started creating the Z8000 BASIC interpreter from the book by Rolf-Dieter Klein. Someone has already got it going and has videos on YouTube, but no links to code or circuit design. He has a homepage in Japanese: http://737mhz.blog130.fc2.com/ and more discussion but still no technical details.
http://www.pofo.de/S8000/ has a lot of information about Zilog's Z8000 systems but they may be too complex for my wishes.