If you look on their website, they have a 580 RWHP 2.3L kit, they also have the 2.9 upgrade.
Lethal Performance 2011 5.0L 580rwhp Whipple Package [LP-2011580RWHPKIT] : Lethal Performance, Performance parts for Ford Mustangs
Whipple 2011 Mustang GT 5.0L 2.9L Upgrade Compressor (Black) [WK-200788B2011] : Lethal Performance, Performance parts for Ford Mustangs
Lethal Performance 2011 5.0L 580rwhp Whipple Package [LP-2011580RWHPKIT] : Lethal Performance, Performance parts for Ford Mustangs
Whipple 2011 Mustang GT 5.0L 2.9L Upgrade Compressor (Black) [WK-200788B2011] : Lethal Performance, Performance parts for Ford Mustangs