Just wanted to 2nd Denisc's point about variation in seats. 1-piece and 2-piece seem to be peppered into production at random intervals. No rhyme or reason, simply what was available at the time.
As for the 2 headlamp cars, I was surprised to hear from PIM that in recent decades they had converted some Geese from 4 lamp to 2. That is a tragedy in my opinion. 4 headlamp was the true design. My understanding is the pop-ups were only to meet road safety requirements.
"There are a few unique elements on very early cars"
I am still hoping to one day see a Goose from the first 10 (or was it 11?) which have the different rear grill. Vertical slots instead of metal mesh.
Also the late cars have what I think is the better parking brake handle. Floor mounted instead of pulling out from the dash.