The rear sway bar is in! I believe it is the 26mm Whiteline sway bar for a 2005 USDM STI. Note: the rear sway bar mounts on the GC8 chassis are different than the GD chassis, so the sway bar bushings I got were not compatible. Lucally for me, I saved my GD mounts when upgraded the rear mounts in my other car! :) I swapped them out, and everything worked great.
Finally I used the Perrin rear end links for the 2005 USDM STI with spherical bearings. The only thing is the clearance seems super close between the rear sway bar and the mud cover for the fuel filler pipe. I'll have to keep my eye on that.
Next step will be to mount up the version 8 JDM STI 6 speed gear box.