In 1980, Theodore returned with AAR and Mosley. They originally fielded the No. 48 Eagle 80-Cosworth DFX at the Datsun Twin 200 at Ontario Motor Speedway. In the race, Mosley retired in 19th place due to a broken cylinder. Starting at the Indianapolis 500 the team replaced the Cosworth engine with a Chevrolet V8. Mosley qualified in 26th place and retired after five laps due to a broken gasket, finishing in 32nd place. the Theodore/AAR team appeared again at the True Value 500 at Pocono International Raceway before parting ways. In the race, Mosley qualified in fourth place and finished in 23rd place after retiring due to a burnt piston. Mosley finished 41st in the championship.