Nice research.
It probably goes without needing to be said, but there has been no player who was a key cog in winning the NCAA championship (mythical or otherwise) and the Super Bowl in consecutive years other than Dorsett. Matt Cavanaugh was Pitt's QB in '76 but the Panthers were clearly a run-dominant team. They went 12-0 with only one victory under 10 points. Dorsett was the focal point and teams still could not shut him down.
Then, after the Cowboys had lost to Pittsburgh in SBX and lost a divisional round game the following year, in '76, Dallas realized it needed a great tailback to win another SB. Tampa selected Ricky Bell out of USC and then the Cowboys jumped at the chance to pick Dorsett at no. 2. He gave the Cowboys instant explosiveness on offense. Do the Cowboys win SBXII with Preston Pearson and Robert Newhouse getting most of the carries? Maybe, as the Cowboys still had one of the best passing games in the NFL and they did have the league's best defense that year (all due respect to Denver), but having Dorsett no doubt gave Staubach a breakaway threat he had not enjoyed since Duane Thomas in the '71 season.