There were a few dealers who sold 67 models as 68. What you see on the title may not be accurate. You need to look up the chassis # to find the actual build date and go from there.
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Keeping it running is better than buying new

Bill;

I know that for the 122, headrest changeover was noted by chassis no. in the parts list associated with exploded assembly drawings. You might check GCP site to see if they note it by chassis no for the 1800 as well.

Cheers

Headrests were required in North American delivered cars for model year 1968.

My '68 122 wagon has the "loop on the floor" - no levers and it is original as the day my father brought it home as a new car.