Motorsport.com understands the Chevrolet teams were supplied with front bars, designed by homologation team Triple Eight, that featured slide-operated mounts for their Gen3 builds.
The idea of the flexible mounts was to dampen the mounts during impact with a kerb, therefore limiting the risk of damage.
However the system wasn't universally well-received by the other Chevrolet teams, with its additional cost a factor, according to one source.
It is also understood to have raised eyebrows on the Ford side given the Mustang features standard fixed mounts on its front bar.
As it stands the shock absorbing mounts on the existing bars have been locked out, while the system isn't expected to feature on subsequent bars delivered to teams.
Triple Eight team manager Mark Dutton confirmed to Motorsport.com that the mounts had been disallowed by the series, while also reiterating that the performance advantage was in lifespan, not downforce.
"The design brief for these was to make everything last better," said Dutton.
"So to increase the life of the front splitter, because it's not generating much downforce, they've got skids on them now, and then if you had a system to allow it to cop and impact, that would have been good.
"Unfortunately, both manufacturers weren't able to do it. We were able to do it in time, the Mustang wasn't. So that we don't get an advantage, we've had to de-tune the car in that area."
"As I said, it's not aero, it's just to make the parts last longer."
Parity between the Ford Mustang and the Chevrolet Camaro is a key talking point on the eve of the first season with the Gen3 cars.
Ford continues to have concerns over the relative aero and engine performance of the two models.
A re-run of the VCAT aero homologation process is expected to take place next week.
In today's all-in pre-season test there were nine Camaros in the top 10, which promptly drew allegations of sandbagging from Ford by some Chevrolet teams.
