Has a College Football game ever ended 31-4?
Exactly once. On September 5, 1987, Miami beat Florida 31-4, and no College Football game before or since has ended that way. When it happened it was a scorigami, the first 31-4 in league history.
That makes 31-4 the 1820th most common final score out of 2,216 that have ever occurred in College Football. One point away, 32-4 has happened 7 times and 31-5 has happened 3 times.