[Lt.Wolf]

The P-51B or even C are American IIIs, the Mustang Mk.III is a RAF British P-51 (Super Mustang) which has less dry HP than the P-51B/C But has a greater WEP boost and supercharger giving a higher boosted HP and far better performance up to the 24,000ft area, above that the P-51B/C are faster and is a far better high altitude fighter for high altitude fights. From what i gather you are asking for the American P-51B/C to have engine of the Mustang Mk.III the only other American aircraft to my knowledge to be given the RAFs Mustang MK.III engine was the P-51 H. Which had the same HP as the P-51B/C but was given a greater WEP, superchargers and various others to give it HP in the excess of 2200 and reduced fuel for greater speeds.

Btw, the P-51C is faster than the P-51B in game due to the Malcom Hood. The P-51D is faster than the P-51 C at low Heights and the P-51C is the fastest Mustang in the game if you go where its optimal is. Therefore if you were to give the B the FM of the Mustang MKIII still the P-51C would be faster. FM discussion on swapping FMs is not allowed here but from what i read perhaps it is just aesthetics and I will allow this for now but will keep a close eye on this.

EDIT: Hawk has the Bird cage external on the aircraft now but to have the birdcage cockpit you would require a cockpit change, is the aesthetics enough or does it have to be on the internal as well?