Mostert will tackle the six-hour IMSA Sportscar race at Indianapolis, known as the Battle on the Bricks, with Kenny Habul’s SunEnergy1 Mercedes-AMG squad.
It marks a return to Habul’s team for Mostert, who last year took a class win at the 24 Hours of Spa with the squad.
Mostert and two-time Bathurst 12 Hour winner Habul are to be joined by factory Mercedes-AMG youngster Jordan Love, brother of Supercars driver Aaron.
Feeney is meanwhile headed for Monza, Italy, having received a call-up to compete in the latest round of the GT World Challenge Europe’s Endurance Cup.
The Triple Eight star will drive in the three-hour race with Mercedes team Al Manar Racing by GetSpeed alongside Oman’s Al Faisal Al Zubair and Austrian Dominik Baumann.
Feeney replaces his Bathurst 12 Hour partner Mikael Grenier, who is contesting the Indianapolis race.
Earlier this year, Feeney opted against being part of Triple Eight’s European GT campaign in order to focus on his Supercars aspirations.
Mostert has been a GT regular in Australia, competing in the local championship with Ferrari squad Arise Racing.