Thats too bad that you moved...but anyways, if you are getting a front clip then you should just swap EVERYTHING how it was in that front clip. There are 2 ways:
1) You could cut a hole in the firewall above the shifter cable exit/entry and feed the harness to the ECU. Then you will need to extend 2 plugs to the passenger side for the ignition plugs right by the Power steering pressure hose. Everything else should plug right in.
2)You could extend the part of the harness about 33" so that it will enter/exit engine bay in the stock location of the USDM harness. This is probably the route that I would go. Make sure to use soldering method and heat shrink wrap all connections.
The only things that I am not sure about are the Fuel Pump Relay and the Fuel Pump Resistor Pack. If you have a ALL-Trac then I dont think that these will be a problem. But since I have a GT-S , it didnt come stock with these components so I had to figure out how to get around this.
There is really no BIG difference between the JDM and the USDM harness, just the location of where the wiring harness enters/exits the Engine Bay.
Good luck,
Keoni