Duratec or zetec?
I'm assuming duratec since the zetec is an iron block.
Top speed has done 650 to the wheels on the 2.5 block with 2.3 crank for a hybrid 2.4l. Your biggest hurdle to surpass that is the head studs. I think the Mazda guys have some ARP L19 studs available. Set you back about $400.