I always though the F1 was the fastest street legal car ever built. I have been reading about the 1988 Twin Turbo Callaway Sledgehammer Corvette and the specs are very impressive.

Twin Turbo V8
880 bhp / 656 kW

The times are impressive also

Mclaren F1 Sledgehammer
0 - 60 mph 3.1 sec 3.9 sec
Quater Mile 11.1 sec 10.6 sec

Top Speed 222 mph 254 mhp

Is the F1 considered the fastest car because it is a production vehicle whereas the Sledgehammer is a modification of a production car?