P51 was designed as a fighter. Only the US Army had its fill of fighter designs. What it had an opening for was a dive bomber. Since the P-51 was so promising at the time they couldn't pass it up. They put dive flaps on the wings and bomb racks underneath. They left off the supercharger because it would be a low alt dive bomber. Probably had a power curve similar to our P-39 in-game.
However, in practice it wasn't very reliable. The dive flaps (top/bottom of wings' center spar) were unreliable and sometimes wired shut in the field so they didn't pop out at the wrong time (so I've read). On top of that they were fairly underpowered with the Allison engines. They had a higher top speed but climb rate was nothing hot. Bomb load was also limited, compared to some other planes of the time. In short, this was a fighter that could only be developed as a dive bomber, so they made it look like one, but it wasn't really one. After they gave up on that and made it a real fighter ("P-51") it became what it should have been, even despite retaining the Allison engine.
It would be cool to see, I think. I think the 4x 20mm Hispano version of the Allison-powered P-51 might also be interesting with a perk price of like 80-100 points or so.
