My father told me that after he got out of the Army after WW2 that these sold in the crate as pictured for about $400.
Looks like from the picture it has forced air, My google fu says this type would be the P-63, the upgraded P39 that the commies loved so much, so it would be one of the last and most powerful, on par with Merlin, or Griffin.
To go way off into the weeds here. None of the american home grown single engine fighters had superchargers, turbochargers, alcohol or water injection....none of that fancy smancy high horse power stuff. Oh they did know about it, but two things really killed it. First was an accident. I think it was a P39, that is a single engine US fighter with the engine behind the pilot, the prop turned by a long drive shaft.....why would they do that you say....well so they could hang a huge 37mm cannon in the nose of the thing. Think a 1930's version of an A10, and that is just how the soviets used them.....everyone else hated them, for many reasons, the car doors being a biggie.
Anyhoo, the engine that gave fantastic performance above 10,000 with all the goodies went kaboom. And the army, remember the army ran the planes at the time, said well lets not do that, besides what good are planes way up there, they can't support the troops on the ground from way up there, our big bomber is super fast has like 10 x 50's on it and nothing will get close to it.
The P51 started out as a ground attack plane, and I want to say they called it the A10, but I am a little fuzzy here. Water cooled planes are not the best ground attack planes, something a little more robust works better, with a roundy engine....no pesky rads to take damage.
But back on my many tracks, the allison just would not fit, too fat, too wide, too long something like that so the rolls got stuck in and the rest is as they say history.
So to come full circle I think $400 seems a bit high for a jeep in a box, about half that sounds better. But we now know why all those crazy boats after WWII had airplane engines in them....all the way up to the 1980's.
I loved "thunder boat" racing, or unlimited hydroplanes. The sound of all those engines flat out was a big rush, after they went to woosh boats I lost all interest.