Fast Freddy-
I believe you are mixing apples and oranges here.
The Wright R-3350 is a "round engine" with the cylinders cooled by incoming air. As stated above the engine has two rows of nine air cooled cylinders. Aircraft using round engines have large frontal areas to enable cooling air to enter the nacelle and cool the cylinders which have external cooling fins affixed to the individual cylinders. The required large nacelle frontal area creates significant airframe drag to the aircraft, but it is necessary to remove the heat of combustion not converted into mechanical work for the propeller.
Interestingly (and as an aside which I always found interesting) my Curtis-Wright Corporation Engineering Handbook, circa 1965, details the “heat balance” for a Wright “Cyclone 18” (believed to be one of the R-3350 variants) at takeoff power, 2500 Bhp/2900 rpm, 0.100 F/A. Of the 13,450 horsepower equivalent energy (100%) provided to the engine via the fuel, only 2,500 hp brake power output (18.5%) is produced and sent to the propeller. Thus 81.5% of the gasoline energy (Btu’s) is dumped overboard as waste heat (exhaust mass flow, radiation losses, oil cooler heat rejection, mechanical losses, etc.). Large surface areas are needed to remove this amount of heat at a rate sufficient to keep metal temperatures from melting.
Your reference to the “Rare Bear” is to a Grumman F8F WW2 fighter which originally had an air cooled round engine (Pratt & Whitney R-2800-W34 Double Wasp, dual row 9 cyl). So it makes sense in the Reno air races the owner would replace one R-2800, 2,100 hp type engine with a larger R-3350 2,500 hp engine.
The reference to a P-51 being repowered with an R-3350 is quite unlikely. Toward the end of the war as the need for faster and faster fighters was necessary (ME 262 jet aircraft were beginning to emerge), aircraft drag HAD to be reduced to go faster. Aircraft drag goes up by the square of the aircraft velocity, so as faster planes were necessary, some way of reducing drag (especially engine cowling) was necessary. Enter water cooled engines which could be cowled much more tightly reducing overall airframe drag. Examples of airframes utilizing water cooled engines include the P51, RAF Spitfires, Hurricanes and the infamous Kelly Johnson P38 designs.
Thus because these aircraft were designed from the onset with much more streamlined fuselages to house liquid cooled engines, it is unlikely one would replace the lower drag cowling configuration of a liquid cooled engine with a much higher drag producing cowling required for an air cooled round engine. IMO.
