How about non-random? A P-38 with Merlin engines. Kelly Johnson had the drawings made for the conversion, and they were available early on. Wright Patterson specifically FORBADE anyone to put a Merlin in a P38[1], but I'm surprised the British didn't try it. That's what made the Mustang flyable; imagine what it would have done for the P38...
[1] While this seems arbitrary and capricious, consider for a moment that they could engine two P-51s for every P-38 and the supply of Merlins was not inexhaustible. The P-38 was also bigger, more expensive to build and operate, and required a larger supply chain than the P-51. A Merlin P-38 would have almost certainly been "better" than a P-51, but the P-51 was good enough, so why take on the extra expense?