the sti intercooler, intake manifold, and turbo don't fit, but most everything else will.
i just picked up 2012 sti struts and springs for it, and woody just grabbed some 2010 sti se struts and springs for his. most everything for 08-10 wrx/sti fits the fxt (except the things i listed above...there are a few other things, but that is the big ticket items).
he doesn't have a turbo, intercooler, or intake manifold, so none of that stuff even matters anyways.
in actuality, even all that stuff works just fine, you just have to swap all of it at once. there is an FXT out in CA that has a full sti swap (engine, suspension, hubs, brakes, wheels, 6-speed, ECU, etc.).