If you're looking to create a hybrid between your non-Boss Mustang and the real deal, take heart: Ford's Racing Performance Parts catalog will sell certain Boss parts.
Available through Ford Racing dealers, those parts include the Recaro seats and the front splitter from Laguna Seca models, along with the wheels from Laguna Seca package, which will be available in black. The gauge pod will also be available, with or without gauges.
Mustangs Daily has the full list of available pieces.