The F4U-3 was to be a high speed, high altitude version of the Corsair. Plans were made for three proto- types to be converted from existing airframes.
Developmental problems persisted with the Pratt & Whitney XR-2800-16C engine, the F4U-1A,BuNo. 49664, was fitted with a R-2800-14W engine and became the XF4U-3B
The F4U-1A,BuNo. 49664, was fitted with a Pratt & Whitney R-2800-14W powerplant with methanol power boost and the turbo charger installed, it became the XF4U-3B