There's a bit of confusion on these because the 1970 style wing was also installed on the early 71 model year cars. The 1971 style wing was used during mid to later 1971 production. No solid cutoff date is known but I've seen the early wing installed on cars as late as December 1970 so at least some cars got them a good way into 1971 model year production.

Here is a 1970 Style on a 71 Demon