QUOTE(mepstein @ Jan 8 2016, 06:57 PM)
It really depends. Early/late doors are different dates than early or late steering wheels, bumpers, dashes, brakes, ect. Sometimes there was early, middle, late
Especially with doors! There are early, middle, and late all within the 73 model year.
I have had 3 73s the first one had the rare middle doors with the late style windows but no side impact beams, the 2nd had late doors, and the one i just recently picked up is a very early 73 build date 2L and has the early style windows (and also appears to have possibly had A-pillar vinyl)
There were a lot of changes though the years, I usually focus on the major ones, the majority of which occurred in 73.
72 - Interior change to movable passenger seat
73 - side shift transmission, door changes, targa changes, strut housing changes, front brake changes, introduction of the 2.0
75 - Major changes to the bumpers. addition of smog equipment
There were a lot of changes through the years but i think most would consider 73 the year of most major changes, unless you are talking visually in which case the bumper change in 75 was the most drastic.