1991 Toyota Celica Replacement?

The engine may not be a problem if it is the same model/size, just a differenet year. The trans is where the problem may be, if thecomputer engien controls were changed between those yrears. Try calling a local salvage yard adn askthem if they are compatible, they have cross-reference books that tell what will fit in what. The engine if the same size/model, you would be best to just swap the engine (Long block) and use the intake/exhaust/all possible exterior parts off old engine to cut down on possibility of issues. Before installation, it would be agood ideaa to replace timing belt and water pump, alot easier out of the car