You might first want to read the story of the 991 GT3 Cup
Porsche 911 991 GT AmericaDate of unveil by Porsche Motorsport North America: August 9, 2013
Premiere: November 16, 2013 USCR test day on Sebring
The 911 GT America is based on the 991 GT3 Cup. It is built exclusively for the United Sports Car Racing (USRC) series and its GT Daytona class for 2014. While the GT3 has a 3.8-litre engine, the GT America is fitted with 4.0-litre unit developing 351 kW. The gearbox is a 6-speed sequential unit with pneumatic paddle shift system. The main visual difference is the rear spoiler made to fit into USRC rules.
Like the GT3 Cup, the GT America has 380 mm steel brake rotors at the front axle with 6-piston aluminium fixed callipers. The rear axle features a 4-piston version.