Mustang Spoiler Delete Plugs
If you are looking to remove your factory spoiler and to fill the factory holes, spoiler delete plugs from LMR.com are the way to go! These plus are designed to snap in place of the holes that are drilled from the factory in your trunk lid. These will help make your trunk lid look smoother and make these holes less noticeable.
These are not designed to be watertight. Some water will still be able to pass around them.