"[6] Superbirds equipped with the top-of-the-line 426 cu in (7.0 L) Hemi engine with a pair of four barrel Carter AFB carburetors (2x4bbl) producing 425 hp (317 kW) could accelerate from 0 to 60 mph (97 km/h) in 5.5 seconds.

[7] Developed specifically for NASCAR racing, the Superbird, a modified Road Runner, was Plymouth's follow-on design to the Charger Daytona fielded by sister company Dodge in the previous season.

The Superbird's smoothed-out body and nosecone were further refined from that of the Daytona, and the street version's retractable headlights (made of fiberglass[2]) added nineteen inches to the Road Runner's original length.

For 1970, NASCAR raised the production requirement from 500 examples to one for every two manufacturer's dealers in the United States; in the case of Plymouth, that meant having to build 1,920 Superbirds.

"Superbird" decals were placed on the outside edges of the spoiler vertical struts featuring a picture of the Road Runner cartoon character holding a racing helmet.

In fact, the 1970 Road Runner was actually quicker in the quarter mile and standard acceleration tests due to the increased downforce produced by the Superbird's nose and wing.

[12] Chrysler memos of September 1969 show that the sales programming staff were preparing to handle 1,920 winged Plymouths for 1970, but published figures say as many as 2,783 were built.

NASCAR's rules implemented for the 1971 season limited the "aero-cars" to an engine displacement of no greater than 305 cu in (5.00 L) or they had to carry much more weight compared to their competitors.

[14][15] The Superbird's styling proved to be extreme for 1970s tastes (many customers preferred the regular Road Runner), and as a consequence, many of the 1,920 examples built[16] sat unsold on the back lots of dealerships as late as 1972.

[citation needed] More recently they have been very steadily rising in price, regularly fetching from US$200,000 to $450,000 however this does vary based on the engine, gearbox and other factory options on the car.