Kellogg's Factory Sets - Where are They?

I've been searching everywhere for Kellogg's factory sets.  These were available via a mail-in offer on the boxes that I was never allowed to send away for as a kid.  There's an interesting part of the story that I won't tell here but maybe if I see readers at a National I can tell you about it in person.

I decided to open this 1981 Kellogg's factory set. 

Now that I've gotten all of the Kellogg's cards except a few variations from 1971 and 1972, I am seeking the factory sets.  Those from 1979 - 1983 are readily available so that isn't an issue.  Earlier ones are another story.

1970 - I've seen football ones more often than baseball.  They sold a bit higher than my budget.  I need to start selling other stuff so that I can get one of these.

1971 - Kellogg's didn't make any for baseball or for their final football set.

1972 - I don't see these ever.

1972 ATG - I missed one a few days ago.  They show up more than any earlier sets.

1973 - these have been available and at a decent price.  This is probably because the 2D cards from packs stay in shape so there is less need to open a factory set to find pristine cards.

1974 - 1976 - I don't see these at all.  This surprises me.

1977 - 1978 - Not available often either, but at least I've seen a few.

If you see these let me know.