Based on a previous question about how slot 7 on the ][ / ][+ was unique as it had two video signals on it that other slots lacked, I am curious why the slot wasn't taken more advantage of. But that aside, I used a few 80-column cards for the earlier machines and seem to recall that they were installed in slot 3 instead of 7.
It makes sense that slot 3 would be used given that it became the standard for the //e, //c and IIgs that followed, but the cards were designed before those machines came out and for the Apples that were from the late 1970s. But that being said, why would they have resided in that slot instead of #7 which had video signals available?
As a side note, I seem to recall that the Videx (?) card wouldn't clear the screen with a 'HOME' command and instead you'd have to pass the Control-L character instead. Then again, my mind is fuzzy 30+ years later :-)