Here is some potatovision proof of the AUI-hacked Farallon EtherMac AAUI #Ethernet MAU mentioned in this post working with #mTCP on an IBM PC/AT (with some help from an old Netgear twisted pair to WiFi adapter).
What I haven't done yet is verify that the AAUI connector still works, but I'd bet it does: all of its wires just pass through the board directly to the MAU.