The aluminum underhood bracing didn't come out till the '76 model year and was part of the Dart Lite option package. Perhaps the hood was replaced after an accident. Underside aluminum bracing would be crimped along the perimeter to the steel top. Look for any signs or replacement parts. The Dart Lite (Sport only) also had aluminum bumper reinforcements. (Big bracing between the actual bumper and the "shock-absorber" style bumper brackets.) That car has those "5mph" bumpers based on the extra carriage bolts near the upper corners of the license plate area. Non-Lite package cars were steel. Perhaps that was replaced from the same car as the hood.