The class structure of global sports car racing is constantly evolving. But the emergence and refinement of the FIA-homologated GT3 platform over nearly 20 years has stabilized production-based classes and created the opportunity for convergence between the IMSA WeatherTech SportsCar Championship, the FIA World Endurance Championship and many other series using GT3 race cars around the world.

The worldwide accessibility and appeal of GT3 has convinced Chevrolet and Ford to join the fray with factory-supported racing versions of the Corvette and Mustang. The Corvette Z06 GT3.R was revealed during 2023 Rolex 24 At Daytona festivities and has been in development with Corvette Racing partner team Pratt Miller Motorsports for the last year. Ford, meanwhile, unveiled the Mustang GT3 roughly six months later at the 100th anniversary celebration of the 24 Hours of Le Mans. Both cars will make their worldwide competition debut later this month in the 62nd Rolex 24.

Mustang and Corvette are joining a deep pool with nine other FIA-homologated GT3 cars that will compete in IMSA’s GTD and GTD PRO classes: Acura NSX Evo, Aston Martin Vantage, BMW M4, Ferrari 296, Lamborghini Huracán EVO2, Lexus RC F, McLaren 720S Evo, Mercedes-AMG and Porsche 911 (992).

Because the GT3 category emphasizes Pro-Am driver lineups, the cars are deliberately “user friendly,” with driver aids including traction control and antilock brakes. Through Balance of Performance adjustments, cars are designed to weigh between 1,200 and 1,300kg (2,645-2,866 pounds); power is regulated to 500 to 600hp and each car must meet specific drag-versus-downforce specifications.

Modern Corvettes and Mustangs require remarkably little modification to be transformed into racing cars. In fact, high-end production versions of both cars feature more powerful engines than their GT3 racing counterparts!

Like every Corvette, the GT3.R is built up from an aluminum chassis produced at Chevrolet’s Bowling Green Assembly plant in Kentucky. The 5.5-liter flat plane crankshaft DOHC V-8 engine — designated LT6 — also originates from the Performance Build Center in southern Kentucky. The racing version of the LT6 shares 70 percent of its components with the standard Z06 engine that originates on the same line. Pratt Miller then fabricates the integrated steel roll cage and side intrusion safety features.

As with the production Z06, the Corvette GT3.R utilizes double wishbone suspension, adding racing-specific springs, dampers and brake components. The racing car features a six-speed sequential transaxle rather than dual clutch eight-speed in the stock Z06.

The Mustang GT3 starts its life on Ford’s Flat Rock, Michigan, assembly plant before being modified for racing by Multimatic Motorsports. The 5.4-liter V8 engine is an enlarged version of the stock Mustang GT’s 5.0-liter “Coyote” powerplant developed by Ford Performance and M-Sport, which is Ford’s longtime World Rally Championship partner.

Aside from the wild carbon fiber bodywork punctuated by an enormous rear wing, the most notable difference between the GT3 and Mustangs for the road is the rear-mounted transaxle with six-speed sequential shift. Multimatic also contributes proprietary dampers and bespoke short-long arm suspension.

North American sports car racing fans will see seven of the new American GT3 machines on the 2024 WeatherTech Championship grid, highlighted by factory-backed two-car efforts from Chevrolet and Ford in the GTD PRO class. Corvette Racing by Pratt Miller Motorsports will field the Nos. 3 and 4 Corvettes in a familiar yellow livery, while Ford Multimatic Motorsports’ entries are Nos. 64 and 65. In addition, AWA will represent Corvette in the GTD class with the Nos. 13 and 17 cars for the full season, with Proton Competition slated to enter the No. 55 Mustang in select events.

With Mustang and Corvette street cars now available for sale around the world, Ford and Chevrolet will also have an international racing presence with their new GT3 contenders. Proton Competition has entered two Mustangs in the WEC, against competition including a pair of Corvettes prepared by TF Sport.

“Mustang is our icon,” said Mark Rushbrook, global director of Ford Performance Motorsport. “We are excited about 2024 for Mustangs in total and what they can do, but especially here in the WeatherTech (Championship) at the GTD PRO level.”

“Our goal is to have Corvettes racing around the world,” added Laura Wontrop Klauser, GM sports car racing program manager. “Our IMSA GTD PRO team is taking the lead on optimizing the running of the car so we can lift all teams to higher performance.”

The Corvette GT3.R and Mustang GT3 will make their official on-track debuts at the Roar Before the Rolex 24, the three-day test session Jan. 19-21 at Daytona International Speedway that also includes qualifying for the Rolex 24, which runs Jan. 27-28 on the same 3.56-mile road course.