right, it is possible as it has been done by MWR, and then some. 384.4 whp.http://monkeywrenchracing.com/mwrmr2_s.html
but yes you will need one tough C2Power tranny or a lot of stock ones changed very often.
and the COST...all of the internal parts, turbo, turbo extras, engine management, factoring dyno time $, installation of internals (assuming you don't do it), sleeving (for longevity), pnp head, installation of the turbo, expensive race clutch, clutch install, tranny...
...tons of suspension work to put the power to the ground...drag slicks (trailor to track or change wheels at track).
oh yes you will want a 10pt or 12pt roll cage with 5pt harness or harnesses.
all means you have to LOVE the Celica and you are a diehard racer who loves to dominate on a track, to some extent.
ok, this is going off topic but for amusement:
you wouldn't be able to beat championship "street" Supras doing 9's or low 10's. but of course you could easily beat stock: Cobra's, M3's, Z06's, NSX's, Viper's, Lotus's (yes and our "soul" brother), and Ferrari's except for the F50. you would be in a driver's race with the F50, Lamborghini's, 911 GT2, and the McLaren F1. not bad IMO. and betting big $$$ with any of these guys you could easily win back your "investment".
so other motivations besides being a Celica fanatic or racer, would be getting "respect" and possibly some dough, in a car which would be an amazing sleeper. and keep the GT badge too.