well you can make your harness work you have to change the idle air conector and re pin it on ecu you will also have to run a wire for the knock sensor and 2 wires one for vtec oil and the other for vtec. this is what you will need engine, trans, ecu OBD2, axles, honda service manual, and maby shift linkage but im not sure on this. You are going to need a little more than you 2500 if you do it your self. you are ging to need a new clutch, water pump, timing belt, dist cap/rotor, plugs, and wires. Maby some other things that i have left out
PS also you dont want to go back to obd1 keep a obd 2 ecu. the motors are the same