Front structural assembly for a vehicle and related engine mounting extensions

The assembly has a longitudinal frame extension (10) connecting a transverse low area bumper beam with a body shell of a motor vehicle. The extension has intersecting ribs (14, 15) extended on an outer face (24) of an elongated tubular body (12). The ribs and the tubular body are made of same material. A ribbed fixation base (17) is arranged at an end of the body. The fixation base and the tubular body are made of same material. A central recess (20) traverses the tubular body, and is opened at longitudinal ends of the tubular body. The frame extension is made of plastic or composite material. An independent claim is also included for a method for fabricating a cradle frame extension of a frontal structural assembly of a motor vehicle.