Lots of guys are swapping 2ZZ's into the MR-2 spyder, that makes for one hell of a fast car.
BTW the sunroof doesn't make much of a weight difference on the celica, unless you have the glass sunroof. they come with a polycarbonate sunroof to keep the weight down, and my sunroof hasn't peeled or anything yet.
If it does peel down the road, I intend to replace it with a Carbon Fiber sunroof panel instead. lots of companies make these to fit a given application.