[TKCR]

The difference with the 67-68, is the seat back foam, from what I remember. It takes a sheet of foam for the back. The seat bottom foam is the same up to 1972.
Now the cover, the 67-68 does not use hog rings like the later seat covers do. They use barrel clips. I’m not sure if that’s what they are actually called, but they are different, not hog rings.
I bought foam for this seat, and the seat bottom foam is the same. The reason why they say the 68-72 foam is different, is solely because they sell it as a set, back & bottom. The back will not work on the 67-68, because it takes just a sheet of foam.