That is a torque rod that applies the front brake shoes. There is a bellcrank and cable inboard on the axle that runs back to the unusual power brake system (33-35 only). This is instead of conduit and cables going directly to each wheel on a mechanical brake system. The Stewart Warner power brake uses the torque of the driveshaft to apply the force to the brake shoes via a clutch system on the back of the transmission and free-wheel unit. The brakes are very powerful but often there is a tendency to creep at stoplights.