Quote:

Reading between the lines, early 71 challengers can have left over 70 production fenders without grill cut outs. 71's produced sometime in Nov switched over to the grill cut out fenders.



I think that's an incorrect way to characterize the change.

1970 & '71 fenders are the same, mid-model year 1971 the "notches" for the "New for '72 grill" started to appear.

Defining the date for the introduction of the "notches" is the question - I doubt it was as early as November '70.