What you can do, is get your hands on an obd0 ecu, take the plugs (sockets) out of it (this will be the end that plugs onto the stock harness). Then get the Harness plugs from a OBD-1 honda (these are the plgus that are on the engine harness etc. NOT the ecu (they plug into the ecu). Its not that hard to make one yourself, just time consuming. once you get those parts, find yourself a wiring diagram for each obd and bring the wires together for each pin.
Your obd-0 O2 sensor is a 1-wire. You need to get your hands on a 4 wire o2 sensor and wire it up. You'll need to find instructions on that as well. You will also need to get an obd-1 dohc vtec distributor and the part of the wire harness that plugs into it. Then you can either cut your existing harness and solder the new dist. plug onto it in teh correct locations or take sockets from an obd-0 dist. and solder them to the plugs you took from teh obd-1 dist in the junkyard. Then you have a conversion harness if you do it that way. I hope I made some sense here....