I don't think it'd be too hard to find sixteen more teams to add to the existing Big Ten, Big XII, Pac 12 and SEC in order to make four super conferences.
Indpendents BYU and Notre Dame are the first two on the list. To keep it simple, you can add in the fourteen teams that are going to be in the ACC and you have your 64 right there.
The question now becomes one of distributing them into the four larger conferences. Realistically, we both know that's not going to happen overnight, if at all, since the conferences operate as quasi-independent entities anyway.
There's also no reason to say the super conferences won't comprise 20 teams divided into two 10-team super divisions. The teams in those divisions play a round robin among their members plus three more games beyond that. The winner of the division goes to the super-conference championship game with the winner advancing to a four-team playoff.
The pre-Penn State/Nebraska Big Ten Conference would have been a Super Division. The same goes for the present Big XII or the Pac 12 prior to the recent additions of Utah and Colorado. Those entities operated fine as conferences, so there's no problem with them doing the same as Super Divisions.
College Football's Division 1-A is soon going to have 125 members. Eliminate 45 of them and you'd have your 80-team entity for football, basketball and most every other sport within college athletics.
The WAC is now down to two football schools (Idaho and New Mexico State), so they could be removed from 1-A. The Sun Belt will soon have eleven members, so you could remove them as well.
That leaves Conference USA, the Mountain West, the Big East and the MAC to provide the remainining programs to eliminate in order to get down to 80 teams.