LSU's average win % as a program is like .655...I'd expect Kelly to do better than that because he's a slightly better than average HC.
I'd guess when said and done he leaves there with .700 win % tops. I mean think about it, he spent close to 90% of his time at ND with his win% lower than the program average...it wasn't until his last 2 seasons he finally poked the top of his head above our average.