I think most years in the late 60s early 70s the date for the new model year started on August 1.
The duster shell I have says July/ 19 / 1974 on the fender tag ....so a few more weeks and it would have been titled a 75 ......I think.
if they started making them on august 1 then it would make sense that orders would start being filled by late august into September by the time they were shipped and dealer processed.
maybe