Wikipedia
STEbus
The STEbus (also called the IEEE-1000 bus) is a non-proprietary, processor-independent, computer bus with 8 data lines and 20 address lines. It was popular for industrial control systems in the late 1980s and early 1990s before the ubiquitous IBM PC dominated this market.
It remains a well-designed standard. Although no longer competitive in its original market, it is valid choice for hobbyists wishing to make 'home brew' computer systems. The Z80 and probably the CMOS 65C02 would be good processors to use. The standardized bus would allow hobbyists to interface to each other's designs.