Beer is riding on an argument.

1971 Dart (Swinger) was not available with a 340 unless you lived in Canada and ordered from one of two dealers. Crestview or Crosstown only. They were a limited run special order from Chrysler Canada and not available in normal production or in the U.S. no matter what codes you used or who you knew.
Technically the Demon was still a Dart and had a 340 through 1972. In fact the 72 340 Demon had DART on the trunk lid...

72 white Demon.jpg