Well, I haven't done it, but I read up on it a lot. I have a set of Arnnie the Farmer decals, and kit, only the car is supposed to be an AWB.
But from what I read, and the way I am planning on it, is cutting out the wheel opening. Then cutting out an opening for where the wheel opening needs to go. Glue the opening in the new location, and filling in the space left over with plastic sheet.
It doesn't seem like it would be too hard to do. I guess a lot depends on how drastic of a body shape and line it changes from where it was to where it needs to go. But that is what Milliputt, sand paper, and filler is for.