Yeah, only the earliest P51 Mustangs had Allison engines, they were almost the downfall of the plane as the Allison's just couldn't perform very well at higher altitudes. Someone had the fore thought to fit a Rolls Royce Merlin to the airframe, and the rest is history. As a side note most of the Merlins that were put into P51 Mustangs were license built here in the good old USA by Packard. Just my 2 cents
Wayne (SAWDOFF) Pearce