How bout dropping a 3SGTE motor, look at super streets issue on TOP SECRETS TOYOTA SUPRA, if a MR2(90-95MR2)motor can fit in a supra theres a good possibility it could fit on a Celica. Dont be fooled by its size, that engine was able to produce 720hp with Greddy turbos according to TOP SECRET, with all of its modifications. The engine by the way is a japanese 3SGTE MR2 motor.
Check out that article. Find it at superstreetonline.com