P-51 Mustang IA:
Four 20-mm Hispano wing cannon
Maybe we could have the british version as a gun package in the game?
The first production contract was awarded by the British for 320 NA-73 fighters, named Mustang I by the British. Two aircraft of this lot delivered to the USAAC for evaluation were designated XP-51.[7] About 20 Mustang Is were delivered to the RAF, making made their combat debut on 10 May 1942. With their long range and excellent low-level performance, they were employed effectively for tactical reconnaissance and ground-attack duties over the English Channel, but were thought to be of limited value as fighters due to their poor performance above 15,000 ft.
A second British contract called for 300 more (NA-83) Mustang I fighters. In September 1940, 150 aircraft, designated NA-91 by North American, were ordered under the Lend/Lease program. These were designated by the USAAF as P-51 and initially named Apache, although this was soon dropped and the RAF name, Mustang, adopted instead. The British designated this model as Mustang IA. The Mustang Mk IA was identical to the Mustang Mk I except that the wing-mounted machine guns were removed and replaced with four long-barrelled 20 mm Hispano Mk II cannon.
excerpt from
http://en.wikipedia.org/wiki/P-51_Mustang