The 2UZ-FE 4.7L V8 engine will simply not fit into the MR2 Engine bay. Also, it weighs over 500 lbs just for the engine (not including tranny)... that's a lot of weight to have in the back of the car. Toyota built the SARD MC8-R (race version of the MR2) but the chassis had to be lengthened to house a twin turbo version of the 1UZ-FE V8 giving out 600 bhp.
If you want high power, the most common way with the MR2 is the build the engine and turbocharge it. Have the engine rebuilt with low-compression pistons, billet rods and crank, add a turbo with a good fuel management system, and then you can easily get up to 500 WHP and the weight and balance of the car will be almost identical to stock.