It is not too bad. You'd need an ecu jumper harness for the ecu. You use the stock obd0 engine harness and modify the plugs for the obd1 motor.
Off the top of my head:
-Re-pin the distributor to accept an obd1 distributor
-you need to extend and change the plug for the coolent temp (fan) switch.
-injectors: you can install a set of obd0 injectors on the obd1 motor and run the wiring as is. If you run the saturated obd1 injectors you will need to bypass the injector resistor box by installing an obd1 power distribution plug.
-install the obd0-obd1 ecu jumper harness
-do the engine specific wiring, i.e) vtec wires, ect...