The Typhoon, Tornado Tempest Fury series tried out almost every possible engine. These engine set ups had to be a "power egg" type otherwise you have two completely different set ups for air cooled and water cooled engines. The wing mounted radiators on later designs were for oil cooling which both engine types required. If someone came up with an air cooled engine that magically fitted into a P-51, much of the radiator system would probably have to be retained to preserve the CoG or a complete re design ordered, like putting the turbocharger there and resulting in another P-47 type.