Goddard, who contested his first full season in the Repco Supercars Championship with Matt Stone Racing in 2021, is without a full-time drive in the main game this year.
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Goddard proved to be an important player in the test, getting a back-to-back read on the two prototypes.
Speaking with Speedcafe.com, the 22-year-old said there were encouraging signs early on in proceedings.
“Firstly, they're actually quite similar,” Goddard explained.
“Obviously they're the same base, it's just a different aero package. Engines are obviously different as well, you notice that a little bit.
“They both definitely feel like they've got reduced downforce compared to the current [Gen2] car, so that's a tick.
“The way the engines are sort of running at the moment, they're performing a little bit differently in different areas. You can definitely notice that as a driver.
“One has more torque down low, one has more torque higher in the revs. Just little things like that. But obviously it's only early days, so that's all getting closer and closer by the day.
“With the aero, there's a little bit of a difference in balance. One sort of favours oversteer [Mustang], one favours understeer [Camaro] a bit more, but nothing you can't tune out of the car.
“There's still a little bit of adjustability on the rear wing, so playing around with that can sort that out. It's all just fine-tuning stuff.
“If they just rolled them out straight away and they were exactly the same I think everyone would have been surprised.
“This is planned for. They're expected to be a little bit different but they're very close. I don't think it's going to take much from the categories to make them on par. That's promising.”
There was one talking point among the drivers who sampled the Camaro that stood out, most noting the lack of visibility.
The Gen3 regulations are such that the silhouette of the race car has to match that of the road car counterpart.
The new Mustang and Camaro have a noticeably smaller glasshouse than their Gen2 predecessors.
Goddard noted the Camaro has slightly smaller windows than the Mustang, with visibility also affected by the styling of the bonnet and nose of the Camaro.
Will Brown and Broc Feeney similarly noted the lack of visibility, making it harder to see inside kerbs.
However, Goddard believes that can be rectified with seating position adjustments.
“Looking out of the cars is slightly different,” Goddard said.
“The Camaro I would say has smaller windows. It's pretty much what you'd expect; the field of vision is a little bit tighter.
“If you're in the right seating position it's fine. If you're a little bit low, the bonnet has got a bit more shape to it. That can sort of get in the way.
“For a full-time driver, that should be fine. They'll put the seat in a position that works.”
Goddard debriefed with the respective Ford and Chevrolet homologation teams, Dick Johnson Racing and Triple Eight Race Engineering, where he gave his feedback.
That, he said, was beneficial to validate his read of the prototypes relative to the other drivers.
“I think it's good having a driver that can jump between the two,” said Goddard.
“You're reading between the lines when you're talking to one driver about one car. When you have someone who can definitively say what the difference is, I think that's quite beneficial.
“I think it was a good process, I think they [Supercars] learnt a bit from it. I think if that can happen regularly at the test days, I think that'll be beneficial for the class.”
Supercars will host another two-day test at Queensland Raceway next Monday and Tuesday.