The corresponding adapter would be the 1107. Model year 2015+ Mustangs are no using adapter 1100 and the 1109. Chevrolet/GMC/Buick/Cadillac/Pontiac/Olds (GM) Prior to the 2000MY most GM products used a rectangular or oval shaped cap on a wide mouthed reservoir.

OE Spec or Performance/Custom: Performance/Custom
Brand: Motive Products
Interchange Part Number: Pressure Brake Bleeder, 1100, 1101, 1103, 1105, 1107, 1108
Manufacturer Part Number: Motive-0260 / 1100, 1101, 1103, 1105, 1107 Adapter
Country/Region of Manufacture: United States