You'll need the bonnet, all piping, a harness that actually works with your car etc. I never saw the flywheels from auto cars so IDK about that. People used to do this a lot more until 2002, when a turbo Impreza was offered in the USA. Since then it makes zero financial sense to do this. I, for one, would not wish the wiring on my worst enemy's dog. But that's just me. I'd sell the car I don't like and buy one that I do. If your existing engine is blown, I'd sell the car anyway if I didn't like it when it ran. Again, just me.