Abstract: The forage receiving container box of a crop transporting vehicle has a shiftable top that may be closed down to compact the box for over-the-road travel without exceeding applicable roading height and width restrictions and may be projected up when the box is prepared for field operations whereby to expand the holding capacity of the box. When the box is rotated from its over-the-road position to its field-operating position, an unloading spout may be swung down from one lateral side of the box to come into alignment with the upwardly and outwardly inclined floor of the box whereby a conveyor extending along the floor and the spout may be utilized to unload the box on-the-go into a truck or trailer pulled alongside the moving box. Projecting up the top of the box or closing it down is coordinated with moving the box between its field-operating and over-the-road positions, particularly with respect to swinging of the unloading spout between its stowed and operating positions.