And all that seemed like a simple task compared to sourcing a left-turning Rolls Royce V-12 Merlin engine. One turned up in a shed in Mexico City. Its provenance is a mystery to this day. Another happy accident was locating the unique canopy, which was found in the possession of a woman in Tampa, for some reason.
End-stage WWII was a hell of a thing. People love to talk about "Manhattan Projects" as if the atomic bomb was the be-all end-all budget-buster development; fact of the matter is both the German V2 program and the American B-29 cost 50% more than nukes. This ridiculous plane came about because hot damn we needed something with a long enough range to follow B-29s and we needed it now so uhh... I guess slap two P51s together?
And then we ended up not having to invade Japan by ground and the skies were largely unopposed and Operation Downfall didn't have to happen and the United States avoided so many expected casualties that we're still awarding leftover Purple Hearts from 1945 that we didn't have to use.