1. You extend the wires on your GZE loom which go into the cabin. (Trying to keep all the colours the same albeit optional on your personal preference) This may take a day to a week.
2. You use the existing AE82 loom hole but you will find that you will not be able to put the new ECU in the factory location. So you can relocate the ECU closer toward the passenger side. (eg. under the carpet)
3. You keep the factory ECU position and use a door handle hole type drill creator thingy (sorry dont know what its called)
and just create a new hole like the half-cut one. But make sure you position it well otherwise it will not clear the heater box and pipes on the interior side of firewall.
Then just plug up your old hole.
Hope it helps.
I chose option 3. As it was the quickest and easiest whilst still retaining factory ECU position.