Look at some of the Mustang sites and you'll see that the, I think, '97 and up Explorers came with GT-40 heads, and an improved upper intake manifold, and are actually an improvement over the base 5.0 that came in the Mustang (by then the Mustang went modular, 4.6, so the 'base' 5.0 that would have gone in the Mustang, but had only the Ex to go to, was essentially a 'Cobra' motor. No, not the 4.6 blown Cobra motor, the 5.0 normally aspirated Cobra motor from a few years earlier.)
Of course the cam is much different, resulting in a torquey, low rev'ing Ex, but I've heard reports of ~300 hp (@ the crank) from an Ex 5.0 with just changing the cam and swapping in the components needed to drop it into a 'Stang (oil pan, distributor, etc)
