SKurj,
You got the wrong specs. Those numbers are for the F4U-1A. Note any listing of combat power with an F4U indicates the use of water injection. I'm not saying that the AH version won't have water, just thAt the birdcage is a trademark of the pre-water models. The max speed of the -1 would be 405MPH and about 350MPH at sea level. Just look at the mil power specs for the -1A.
However the upside is that the -1 without water is much lighter.
F4U-1 (no water)
Empty is 8762lbs
Normal fighter load= 11,161lbs almost 1K less than the -1D
Full main tank weight= 11,515lbs 500lbs less than -1D
Full internal fuel = internal wing tanks= 12,676LBS
So the F4U-1 no water will be slower than the 1D by about 10 to 15 MPH but will handle like a Hellcat or better.
Also keep in mind that the flaps will be fixed along with the F4U-1D climb and F4U-1C weight. But the really big news is that Pyro promised 1 more thing when he fixed the 1D and added the -1. The F4U-4!!!