There are/were
apparently a number of Apple LocalTalk cards made
for PC usage. One of them is the PC MacBridge by Tangent Technologies -
now defunct - which is a short 8-bit card based on the Zilog Z8530APC
chip. A google search will disclose multiple others also.
I have a native Apple LocalTalk ISA card manufactured by Apple. It does an
excellent job and the PC communicates seamlessly with the Macs in the
apartment.
Since the thrust of this topic is find a board that can be used
to do IBM BISYNC communication, would you happen to know what
chipset is used by the board? It would be hard to use it if
no one knows how to write software for it...
-dq