MAX shows a pic of the GS plate. Narrower in the back, no cutout for the drain plug (makes sense as the smooth sump has a rear-facing drain). Most likely the difference originated with the different centerstand on the GS. Don't know if it's shaped differently around the exhaust or anything.
I don't see why you wouldn't be able to retrofit the GS system to the G/S. System being plate, sump and pickup.
EDIT: actually I don't think it is narrower.