A lot of people have thought about it but bobody has done it. Ford Engineer say that the currently available V8's will not fit in the Explorer Sport or Sport Trac engine bay. I don't know if it's a length issue or a width issue, or some other interference. Some people here think it should be a bolt in swap, however since nobody has actually done it, I doubt that it's that easy, especially when the engineers say the current V8's will not fit.
I'm sure it can be done, but the question is How much cutting, modifications and fabrication will be required to make the engine fit. "Is it worth the time and expense for as little as 30 HP and perhaps drivability issues"?
...Rich