This is a 67 that I restored in the 90's for my son Eric to drive to school.
It was a frame off and rotisserie restoration. It ended up with a SBC Chevy 350 and a 350 transmission one of a few that I should have kept.
I dont know about those old Chevelles but in some cases those small vent windows are not year specific.... but may have more todo with where the vehicle will be sold.... Ive had several Ford Bronco IIs over the last 20 yrs and every one I find in Canada does not have the small vent window... but on forums most every US model I see does have them... regardless of the model or the year it was built. I dunno why... just the way it is... one piece windows were the norm in Canada but the two piece windows were the norm in the US.