And on the horizon? Yes, the mighty P-75....

Well, perhaps the Bell P-63 Kingcobra, which didn't have the P-51's
performance, but did have the two stage supercharger that was originally
intended for the P-39, and might have performed well under combat
conditions. It was capagle of carrying two large external fuel tanks.
http://en.wikipedia.org/wiki/P-63_Kingcobra

Brian