Originally Posted by C3luisMx
...I have no notices about ´70 leaving the factory with a ´69 front end...
They didn't. You've got a replacement front end on your '70.
Xpoc454: "Early" and "late" usually apply to a specific running change made during the production run. For the specific part you want, check the revision dates at the bottom of the AIM page to see when a part might have been changed on the assembly line.
In Tim's example of the vent knobs, the AIM will probably show the round ones with a notation of the old part number for the '68 knobs and the date the part was revised.
Rule of Thumb only: the round vent knobs could
have been in production before the AIM revsion became effective, but the date will get you in the neighborhood.