Not sure if many people have. Why move it 8"? If your going through the effort of moving it, get 10-15 extra feet of 2 gauge cable and put it in the back...?
You will have to most likely lengthen most of the cables even moving the short distance.
But the biggest reason I dont think you will find any one here who has done it is the height tolerance. I have not measured it, but from memory a standard car battery will have a higher profile than the air box so the top leads will hit the hood, which is not good. You could go with a solid cell like an Optima and put it on its side, but still not sure on the tolerance between the top of the transmission/driver side motor mount and the hood.
But that brings me back to the first question, why not keep it in the same location or run the power cable to a battery box in the back?