In earning the crown, he saw off three-time and back-to-back title winner Shane van Gisbergen, who moves to the United States this month to pursue a career in NASCAR.
Van Gisbergen won on his NASCAR debut and made a second appearance in the top tier at Indianapolis in August, where Kostecki was in the field for his own Cup Series debut, with Richard Childress Racing.
Childress himself has spoken openly in recent weeks about fielding Kostecki in as many as five races in 2024, including an oval, and the West Australian cut his teeth in the K&N Pro Series as a teenager.
NASCAR is therefore an obvious avenue which he might pursue but, despite now having one of the major Supercars accomplishments in his pocket, he is eyeing others at home – and a repeat of his championship feat.
“I want to win it next year,” said Kostecki.
“And obviously, there's Bathurst and a few other races I want to win as well.
“So, I'll just take it as it comes, but yeah, I've got plenty of unfinished business here.”
Until this year, his third as a full-timer in the Repco Supercars Championship, second place was his best result in any race in the category's top flight.
“I believe it; I mean, the teams' worked incredibly hard – as well as all the other teams in pit lane – but we really just got our act together this year and got on top of the new Gen3 cars quite early.
“Honestly, it's been a journey for us over the last three years.
“Obviously, a bit of experience on my behalf and my engineer's [George Commins] behalf as well – just working well with each other – and having Will [Brown, team-mate] there as well, pushing me along for the whole year, was really important as well.”