I realize that this isn't what you are trying to determine here, but there would have been a fierce debate over which teams to include.
Miami and Washington would have been obvious as both were undefeated and conference Champions (BigEast and Pac respectively) but after that it would have been highly debatable.
Florida was #3 in the December 2, 1991 AP Poll and SEC Champions at 10-1. That is the argument for the Gators. The argument against is their 17 point loss to #16 Syracuse. The Orangemen (as they were still known back then) got annihilated by the Seminoles in Tallahassee, lost to East Carolina at home, and somehow avoided playing Miami despite both being in the Big East.
Michigan was #4 in the December 2, 1991 AP Poll and BigTen Champions at 10-1. That is the argument for the Wolverines. The argument against is their 20 point home loss to Florida State.
Florida State was #5 in the December 2, 1991 AP Poll and a 10-2 independent. The argument against them is that they had just lost back-to-back games to Miami (by a point, one of the famous missed FG games I believe) and Florida (by five points in the Swamp). The argument for them is that those were their only two losses and both were considerably better than Michigan's or Florida's losses. Their SoS would be through the roof with games against #1 Miami, #3 Florida, #4 Michigan, and #16 Syracuse.
Penn State was #6 in the December 2, 1991 AP Poll and a 10-2 independent. Their SoS wasn't as good as FSU and one of their losses was to an uncharacteristically weak (3-8) USC along with a close loss to the Hurricanes in the Orange Bowl (Stadium, it was a Miami home game).
Iowa was #7 and a 10-1 BigTen co-champ but they got drilled at home by the Wolverines so they wouldn't have been a factor.
Alabama was #8 and a 10-1 SEC co-champ but they got drilled in the Swamp by the Gators so they wouldn't have been a factor.
aTm was #9 and a 10-1 SWC (remember them?) Champion. Their only loss was early in the season by one point on the road to Tulsa which finished the year ranked #23. They would have had an argument as a Power Conference Champion with only one loss and that loss being arguably better than either Florida or Michigan. Their problem was that their best win was over an 8-3 Baylor team that received votes in the 12/2/91 poll but wasn't ranked. The problem for them was that Texas (5-6) and basically the entirety of the SWC had weak records that year.
Another interesting memory from those days was how many teams went into the Bowls with at least a somewhat plausible chance at the NC:
- Miami played #11 Nebraska
- Washington played #4 Michigan
- Florida played #18 Notre Dame
- Michigan played #2 Washington
- Florida State played #9 aTm
- Penn State played #10 Tennessee
- Iowa played nr BYU
- Alabama played #15 Colorado
- aTm played #4 Florida State
- Miami: Simply win and root for Michigan or at least a close Rose Bowl.
- Washington: Win and root for Nebraska.
- Florida: Win and root for Nebraska and Michigan.
- Michigan: Win and root for Nebraska and Notre Dame.
- Florida State: Win bit, root for Nebraska and Notre Dame and hope for a sloppy Michigan win over Washington.
- Penn State: No real chance.
- Iowa: No real chance.
- Alabama: No real chance.
- aTm: Win, root for Nebraska and Notre Dame, and hope for a sloppy Michigan win over Washington.