The main Mustang lineup remains offered in Base, Premium, GT, GT Premium and Shelby GT500 versions, with Coupe and Convertible versions of each trim. Coupe models get a 50/50-split fold-down back seat to accommodate larger cargo, and the trunk is surprisingly spacious. Convertible models give up some seating space in back, but they still have ample space to either cruise with back-seat passengers or tote around the baggage for a weekend road trip. The Convertible's soft top is power-operated and quite simple to operate, stowing in less space than retractable hardtop designs. It's also surprisingly quiet inside with the top up. Even base Mustangs come with cruise control, keyless entry, power windows, locks, and mirrors and Ford's customizable MyKey system. Premium models add 17-inch machined aluminum wheels, upgraded leather bucked seats, upgraded trim, an ambient lighting system and a premium Shaker audio system with satellite radio and Sync Bluetooth connectivity for hands-free calling and audio connectivity. The 2012 Ford Mustang Shelby GT500 remains the highest-performance street version of the Mustang. It's powered by a 550-hp, 5.4L supercharged V8, with a 6-speed manual gearbox, 4-wheel vented disc brakes with Brembo front calipers, a stainless-steel exhaust, and other upgrades and comes with most of the same interior features as Premium models. Ford has tested it to 60 mph in just 4.2 seconds. In the Boss 302, the GT's engine has been given revised camshafts, boosting power to 440 hp. It also has a special intake system and new quad exhausts to reduce backpressure. To help handle the power and the demands of the track, the Boss 302 gets a stronger clutch for its short-throw, close-ratio 6-speed manual gearbox and the Boss 302 gets a 3.73 performance rear axle and limited-slip rear differential. To aid handling, the Boss 302 gets adjustable shocks, stiffer anti-roll bars and stiffer springs. Unique traction and stability controls and special 19-inch black-painted lightweight alloy racing wheels and Pirelli PZero summer performance tires round out the package and eleven pounds of sound insulation are removed, compared to other Mustang models. Additionally, a Torsen limited-slip rear differential and Recaro sport seats are offered together in an option package. A Laguna Seca package for the Boss 302 brings an even more serious package, deleting the back seat entirely and adding Recaro cloth sport seats, brake cooling ducts, a front air splitter, the Torsen limited-slip differential, a gauge package and further changes to springs, wheels and tires. The rest of the Mustang lineup returns with either a 305-hp, 3.7L V6 or a 412-hp, 5.0L V8. V6 and GT models can both be had with either a 6-speed manual or 6-speed automatic transmission. Across the entire Mustang lineup for 2011, steering effort is now driver-selectable; with comfort, normal and sport modes, the electric power steering system. A host of trim and appearance options, such as special wheels and paint striping, can give the Mustang an individual appearance. Other standalone options on the Mustang include HID headlamps, and a large glass roof that brings some of the advantages of the Convertible with all-season weather-tightness.