Yes you can put the GTE engine in the car with an auto, but you'll want to use the auto that came on the Supra. The mkIII car has the 7m-gte engine, completely different. Your best bet is to turbo the engine that's in the car.
www.Toyomoto.com www.Sound-Performance.com www.SupraStore.com all have turbo kits to do this.
SR