Dan,
I think what AMD did was make a 70 only and a late 71 only
The late 70 early 71 may have changed and they maybe did not make that one.
See my picture of the stamping crease.
Bob

rsz_img_3167.jpg
Mom & Dad let me buy a brand new 70 Challenger R/T 440 Six-Pack Super Trac Pack when I was 17

(Robert what is a 440 Six-Pack)