NASCAR didn't really ban them for 1971 as many people say but that was their intention.
They didn't want people to run them anymore so they put a 305 cu in limit on them.
One team thought they can still be competitive and got Keith Black, a well known top fuel drag racing engine builder to build a 305 for it
here is a cool story on "The Last Wing Car"
https://www.hotrod.com/articles/found-last-wing-car/