I searched but could not find this topic covered...for the trunk filler board I have observed "early" 67 using a fairly thick Masonite type product that is screwed down in two location. "Late" 67 and 68 is more of a cardboard material, and if I recall had some bent tabs to hold in place, no fasteners. Any corrections to that observation? How about dates for the change?
I did find the attached Phillips screw with captive washer on 7R01C126 a week or so ago. Looking through my pictures, I see the same thing on 7R01C140, as well as 7R01T145.
I see that 7R02T170 has the later version, as does 7R03C188.
It is hard to find this detail - a lot of them are missing, or covered with mats. I did find some later model pictures with no mat, no board, and what appears to be no holes in the floor, indicating that the snap in cardboard type was used.