Well, since no model of the P-51 or P-47 is specified, I will go with the P-47.
The "N" model of the P-47 actually saw combat in significant numbers and could beat the tar out of any P-51 model that saw action.
Additionally, I think that at very high altitudes, say above 32,000ft, the P-47D outfitted with the paddle blade propeller could probably take a P-51 as well.