i dont tihnk youll find a loom and ecu, your best bet is to ring a few importers , or go aftermaket ecu, although an aftermarket ecu isnt a good option if you just want to get it running and sell it. youll be able to use the 162 fuse box's etc as ive used mine with the 185 3sgte but im using an aftermarket ecu so u may or may not run into problems there. ask in the 162 dedicated thread in general car talk a few have done this conversion and will be able to give u the info your after
or another option would be to buy a gen 1 3sge put it in use all ur gear and sell it and sell the gen 3 3sge youd probly come out ahead doing it that way