I'm just saying that the f4u-4 was rated at 446 mph on the deck and it does more then 50mph less then that in the game
You're confusing ground speed with speed on deck. Just because article says prototype achieved "an average ground speed of 405 mph" doesn't mean it could fly that fast on the deck. It just means it was measured on the ground. Same mistake is on Vought's website.
Ground speed = true airspeed - + wind speed
It doesn't say at which altitude, but it probably was around it's best.