itr rods and crank wont fit into that block without a deckplate and some major machining/clearancing (the kinda stuff even a skilled engine builder would shy away from). For that kinda work you're better off starting over with a new engine.

If you wanna keep up with an sti at the track, you'll probably need more than what a stock itr/ctr has to offer. Sounds like its time for a full build-up