yeah 02-07wrx, i'm sure sti will also fit but just to think about the wider track of the sti makes me thing that it wouldn't be perfect for your application.
I just installed Cusco 22mm front sway bar to my GC w/WRX x-member swap yesterday, ordered bracket from dealership $10/pair, and threw the paper in the garbage. I'll dig it up tonight for you to get P/N. If you just crawl under or take a quick peak to see there's a STUD sticking out from the subframe (need a nut to screw on,) the other side of the clamp is thread with 1.50mm so you need a screw about 1 inch long.
WRX bushings/bar(20mm f/r sedan) is fine and cheaper but if you use aftermarket larger Whiteline or Cusco it's more expensive. Bushing should match sway bar size.
Sway Bars at RallySportDirect.com