You use the h23a wiring harness. I am currently running the p14 myself, until I get some time this weekend to wire the two VTEC wires up. It runs decent enough, with a slight bit of knock.
You do have to change the ECU for manual and auto. You'll be needing the 5sp p13 anyways.
You use the external coil from your h23a. It plugs right in. There is no rewiring anywhere except for the VTEC solenoid and pressure switch.