It's not a Zetec or a Duratec, it's an I4 from the same family as the Galaxy/Scorpio engines. It's like the DOHC in later Sierras, but with a unique 16v head. The engine is unique to the RS2000. It's not a straightforward swap by any means and for the gain in performance I would stick to the engine you have as I assume it will be a 130ps.