The Mustang had an interesting history, it was the RAF who had them first, with unsupercharged Allisons, for ground attack in the desert, they were then fitted with Packard built Merlins, the factory which featured in the Requiem for Detroit film was where they made them. Some later Marks of Spitfire had Griffons rather than Merlins. The laminar flow wings of the P51 made them both fast and at lower speeds economical, which made them ideal escort fighters.
Damon.