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You have to drill 4 additional holes for the front studs. The rear studs fit in the stock holes. The OEM spoiler comes with a transparent template that you lay on the trunk lid. Between the 8 studs and the 3M tape you'll lose the trunk lid before the spoiler comes off.
You have to make sure you really want the LS spoiler since it is a commitment. It does make a huge difference on the track. The GT500 spoiler uses the existing holes so you can change it back to stock for resale down the road. I think the GT500 spoiler downforce is something like 2/3 of the LS spoiler downforce.