Wanted to add something I remembered from my 5.0 explorer days. There is a severe restriction in the exhaust system that really hurts performance. The explorer got GT40P heads with a different spark plug angle. Traditional 302 headers won't fit and the only bolt on, explorer 5.0 GTP header, made by TorqueMaster I think, runs over $600 for shorties.
I'm really interested in building an Explorer 302 for a project some day. Ditch the factory head for an aluminum aftermarket version but keep OBD2 in place for modern drivability.
OBX made a knock off of the Torque Monster headers for half the price. Havent seen any on eBay in a while.