Vehicle body front portion assembly with improved fastening and position adjusting means, and vehicle provided with such an assembly

The assembly has a flexible beam projecting from its front side. The beam has one end fixed to the front side and another end (43B) connected to a wing part (5). A centering and guiding part (71) is fixed on a front part structure, in an adjustable position, along three axes. A guide rail (93) and an additional rail (95) guide the wing part with respect to the part (71) to ensure a sliding connection along longitudinal axis. An independent claim is also included for a motor vehicle including a front part assembly.