The Plymouth Superbird was an automobile that existed for one reason only - to win at NASCAR.The Superbird was basically a modified Plymouth Road Runner, but it was realized that while it was alright on the street to have the 'aerodynamics of a brick' (typical of most American cars of the period), something a little better would help at high racing speeds. So, following the lead of the previous year's Dodge Charger Daytona, the Superbird sported an aerodynamic nosecone adding nineteen inches to the length and containing retractable headlights, a slightly smoothed-out body, and to counter a tendency to lightness at high speed, a rear wing was mounted high on very tall tailfins. The reason for the fins was mostly to give clearance beneath them to lift the trunk deck lid, but it probably didn't hurt that it put the wing into less disturbed air.
NASCAR banned the Superbird and all the other aerodynamic speedsters in the 1971 season, concerned about dangerously high speeds and that the cars didn't look all that 'stock'
Does anyone knows its performance figures?