There's some info in the Ginter book on the F8U-3. It was a 1957 proposal for a strike version for the RAF (in advance of the GOR.339 requirment that lead to TSR.2) offered jointly by Chance Vought and Rolls-Royce. It seems to have been pretty sketchy: the only hard details were the Conway engine and a 2000lb "special store" (i.e. a nuke) semi-recessed under the rear fuselage. Everything else was vague statements about UK systems and weapons.
If the RAF had been in the market for this class of aircraft, it's hard to imagine them picking this over the F-105 or the Hawker P.1121. Had an import been acceptable, then the Thud would have been a low-risk off-the-shelf buy, whereas if a new development was indicated then the "Strike-Crusader" would have needed as much high-risk new avionics as an all-British project. As it was, the RAF thought it wanted something bigger, which lead to the TSR.2 debacle. RN plans in 1957 had strike being done by the Buccaneer and intercept by the SR.177, the latter surviving the infamous White Paper before being cancelled at the end of the year when a German order failed to materialise.