As far as design :
People are forgetting one thing : application notes. Most vendors
have application notes that give a working sample implementation using
their chip. For instance, National Semi's AN-479 has full schematics,
a materials list, and a PAL program (for the PAL that does shared memory
arbiting and address decode) for an ISA 8390 board (AUI / thinnet,
jumper selectable). If you were to go with a shared memory 8390
implementation you could take this design, and write a new PAL program....
In any case, the analog side (what scares the non-EE's among us)
with the pulse transformers, etc would allready be done for you.