I went the rout of using the JDM ecu and harness.
OBD II, of course
Will it pass U.S. OBD II plug in inspection/emissions check, No.
Not all states require, check your local listings.
JDM ECU won't send 'ready bit' that US OBD II tests look for.
Keep your USDM ECU and flash with JDM map (No AVCS) to get thru US OBD II plug in inspection.