The single game rushing record is 305 yards held by Jose Medina of the Philadelphia Bell way back in 1974.
In fact, Medina rushed for 303 yards in another game in the 1974 season and is the only player to ever rush for over 300 yards in a game.
He ended up with 1,526 yards rushing for the season which is only the 12th best.
The single season rushing record belongs to RB Bruce Fine of the Chicago Blitz in the same 1974 season. He rushed for 2,056 yards, avering 5.4 yards per carry and is the only 2,000 yard rusher in league history.
Medina and Fine finished ranked 11th and 9th in rushing but neither made the Hall of Fame.