I dont know on the gears. I do know that I had read that the tail sections were nearly the same, the diff being that the STI variant has the hole drilled out for the DCCD control wiring. It would be great if you could just use the Spec.b gears. Tehre is A DCCD up for sale on nasoic right now for 645 shipped.
http://forums.nasioc.com/forums/show....php?t=2213237