Never having been involved with a GDA conversion, I don't know for sure. I'd imagine the rear NA loom (rear doors, tail lights, fuel pump) would match the turbo front loom (engine, dash, hand brake, lights etc). This does mean pulling out the seats, carpet, cluster, dash etc down to the metal of the firewall. Doesn't take very long.
check out my gif of my car.. as you can see, the majority of the loom actually sits behind airboxes that need to be pulled out.
http://jester.egn.com.au/retsej/interiorx.gif
as for the other bits... after market fuel pump ($200 or so) to replace the 6 year old NA one, China 3" full exhaust ($650) to bolt up to the turbo or a stock one if you can find one, and most likely being a Jap import half cut, personally I'd have it reflashed (verso $990) to make it safe on aussie fuel running the 3" exhaust.
You'll likey be able to utilise the rear end, with different shafts to suit the different diff (what ratio gbox does the RS have?)
Cost wise.. your still better off pursuing a 2.5 long motor
