Ford was granted a revised aerodynamic kit ahead of the weekend featuring modified side skirts, a revised rear wing position and angle, and smaller side mirrors.

A 30ms shift-cut offset has also been introduced following the parity review.

Supercars’ decision to allow changes to the Mustang in the name of addressing an apparent straightline speed deficit to the Camaros was met with resistance from GM.

Triple Eight and PremiAir Racing have publicly expressed concern that the specification has been changed from that which was signed off following wind tunnel testing in the 2023/24 off-season.

However, the revised package consists of parts previously used in 2023 and was also tested in the Windshear tunnel.

Ford Mustang aero parity changes in photos

The package is said to cut drag while also marginally reducing the car’s overall downforce, shifting its aero balance rearward.

Ford drivers and teams have been reluctant to declare the changes a net improvement, with Kostecki saying he’ll learn more during today’s race.

“I haven’t raced any cars yet, probably the true test will be in the race, but honestly it feels the same to me,” said the Dick Johnson Racing driver, who was the driving force behind the change.

“The most optimal package was selected in the wind tunnel. We’ve gone to a less optimal one to try and improve the straightline, so we’ll find out [in the race].”

‘Plenty of tricks’: Kostecki’s cheeky Whincup sledge

Ford drivers have topped five of the eight track sessions ahead of the 500km race, while six Mustangs and four Camaros contested Saturday’s Top 10 Shootout.

Kostecki was fastest in regular qualifying before finishing third in the Shootout behind Camaro drivers Broc Feeney and Cam Hill.

“I knew going into the Shootouts it was going to be quite tough,” said Kostecki.

“We weren’t very good out the gate on first lap on greens and had to wait for a bit of car temp, so we’ll learn from that. But honestly, it’s all about focusing on the race.”

Further parity work is expected to take place before the Bathurst 1000, with Supercars having pledged to undertake a study into the impact of barometric pressure on engines.

Ford’s changes are largely aimed at ensuring its cars are competitive in the Great Race following two tough years at Supercars’ crown jewel event for the Blue Oval.