without forged internals you will be very limited in the forced induction aspect of your build. I'd say E85/meth it and call it a day. Your car is way too beautiful to sink a ****-ton of money into it just to have the beast throw a rod one day.
IMO I'd try and find a donor WRX that has been totaled (preferably from the rear
) and swap the drivetrains. Much less headache. If you ever mess up or go crazy with your transplanted build, you will always have your well taken care-of 2.5i drivetrain to fall back on.
Beautiful, beautiful pristine example of a 2.5i... keep it that way!