One difference between the Z66 and Z71 RPO codes is that the Z66 is only in two-wheel drive and the Z71 is four-wheel drive.
The Z66 is the Premium On Road Suspension package, which translates to a better handling suspension like an SUV would have. The Z66 package consists of the following: Traction control, a limited-slip differential, a high-capacity air cleaner, rubber floor mats, an upgraded suspension with self-leveling rear shocks, and P265/70R17 tires. The RPO codes for your vehicle are usually on the inside of the passenger glove box door. Other locations to look for RPO codes include the driver side door jam, spare tire cover, passenger side pillar, or the trunk lid.
In recent news from GM, Chevrolet announced today that the 2014 Corvette Stingray's new LT1 6.2L V8 engine is SAE-certified at 460 horsepower at 6,000 rpm and 465 lb-ft of torque at 4,600 rpm, with the available performance exhaust system. Engine features include things like an advanced oiling system with oil-spray piston cooling and available dry-sump oiling, and an engine-mounted, camshaft-driven fuel pump to support the direct injection system that the engine has. The 2014 Corvette Stingray coupe will go on sale this fall, with a convertible following by the end of this year.