The 19-year-old grandson of team owner Joe Gibbs from Charlotte, North Carolina, will be substituting for Kurt Busch for a third consecutive Cup Series weekend at the Irish Hills.
The 40-year-old Allmendinger from Los Gatos, California, led all but 20 of 62-scheduled laps en route to his third Xfinity Series victory of 2022 at the Brickyard.
The 2020 Cup Series champion was awarded his fourth victory of 2022 at the Tricky Triangle following the post-race disqualifications of race winner Denny Hamlin and runner-up Kyle Busch.
The 24-year-old Gragson from Las Vegas, Nevada, led a race-high 43 of 90 laps, including the final 21, to record his third Xfinity victory of 2022 at the Tricky Triangle.
