Check this thing out.
http://web.archive.org/web/19970810203842/http://www.mahoroba.or.jp/~bouno/10mram.htm (http://web.archive.org/web/19970810203842/http://www.mahoroba.or.jp/~bouno/10mram.htm)
Great find Neko68k !
I translated the web page from Japanese to Engrish and converted the attached schematics from PostScript to PDF.
10M RAM Board
http://nfggames.com/X68000/Schematics/10M%20RAM%20Board/ (http://nfggames.com/X68000/Schematics/10M%20RAM%20Board/)
Keep the scene alive !
Eidis