Originally Posted by Fluid
No way. The heads are completely different and the engine management would be impossible. In addition, since the timing belt or cams drive the injection pump you would have to somehow make your own timing belt or camshaft.
2nd. Without some way to manage the injectors it would be impossible. Maybe if you had a pumpe duse engine (so it wouldn't mess up the timing belt), had custom engine management, a custom common rail line, fuel pump, and injectors. By that point, you could probably buy a brand new car with the common rail engine.