As I know the Gallardo Sport Package has the P-Zero Corsa fitted on it. However, does anyone know if the size is different?

Good question, as I have been trying to buy P-Zero Corsa for my G and they are not listed to come in the factory G sizes as yet. Perhaps Pirelli will tool up for the stock Gallardo sizes. I would expect the sizes to be the same, in order to make sure the all-wheel drive and stability management continues to operate properly.