ok easiest things...get it running on a factory ECU but you will have to buy a maf which might be a junkyard part from an old NA subie (I can double check with a few old JDM subaru guys I know).
Pick up a wrx/sti manifold (same thing), STi uppipe or gut a wrx uppipe, get a td04 but a VF39 (factory sti) would be much better. For IC just get a used WRX one.
Downpipe will need to be custom and would be easiest as a dump tube. Either that or make your own manifold/uppipe and down pipe and plumb the turbo in the rear of the car/front of the motor. Many subie motored sand rails do it this way.
Radiator will probably be easier doing one off...how do you plan on running it? (location )

Check nasioc and you can find cheap factory parts...


AC would require custom AC lines for starters.