Has a College Football game ever ended 78-7?
Exactly once. On November 10, 1928, USC beat Arizona 78-7, and no College Football game before or since has ended that way. When it happened it was a scorigami, the first 78-7 in league history.
That makes 78-7 the 1820th most common final score out of 2,216 that have ever occurred in College Football. One point away, 79-7 has happened 3 times and 78-8 has happened never.