well its more logical just to drop a LS3 in it. 6.2L 450 ftlbs torque and 460HP. besides brad will have his conversion car up and running alegedly by junish.
2.5 liter STi motor from a Subi would be more in keeping with the cars balance - easy to get 350 to 400 HP from those motors. Too bad know one has looked at that route yet.