The 37-year-old Enfinger from Fairhope, Alabama, overtook Zane Smith during an overtime attempt to snap a one-year winless drougth and become the first Playoff competitor to transfer from the Round of 10 to 8.
The 31-year-old Kligerman from Stamford, Connecticut, led a race-high 56 of 67 laps, including the final three, en route to his third Truck Series career win.
The 22-year-old Gilliland from Sherrills Ford, North Carolina, spent his final off-weekend period from the NASCAR Cup Series by celebrating a Truck Series victory at Knoxville, Iowa.
The 2018 Cup Series champion led 20 of 242 over-scheduled laps and prevailed in a late crossover battle with Kyle Busch to capture the inaugural Cup event in Madison, Illinois.
The 19-year-old Heim from Marietta, Georgia, prevailed over a late caution, a preferred lane choice and an overtime shootout to claim the first of three Triple Truck Challenge bonuses at Gateway.
The 22-year-old Smith from Huntington Beach, California, will be filling in for Buescher, who will not compete at Gateway following a positive COVID-19 test.
Ross Chastain capitalized through two overtime attempts and a late incident involving teammate Carson Hocevar and Ryan Preece to fend off the field and win the North Carolina Education Lottery 200 at Charlotte Motor Speedway on Friday, May 27.