Sourcing them is hard. Maybe a pull from some other board that's been designated "parts"? I looked at some boards I have (where some idiot shaved off all the metal from the edge connectors) but no 8235's there. If you're driving a PDP-8 bus, maybe a pair of 74*756 for "A" and a pair of 74*757 for "B" would allow a low parts count replacement? (I think one of the 757's enables is active high, though.) Are you looking to repair a TD8E, specifically? Those look like simple B/!A switches, activated by SDRD and SDRC instructions. If you are working with an existing M868, that limits the desirable substitutions, because you wouldn't want to rework every darned thing. (OTOH, E01 has the spare inverter needed by the 74*757. You could socket E01, E05, E10, and E15, and make a little daughter card to plug into the sockets.) Vince