Abstract: The header or platform of a harvesting machine such as a combine is tiltable laterally relative to the throat of the combine about a lower, fore-and-aft extending pivot located adjacent a normally lower, forwardmost section of the throat so that variations in ground contour between opposite lateral ends of the header can be accommodated. A hydraulic piston-and-cylinder unit provides remotely operable, powered tilting, and a special adapter assembly renders existing combines having non-tilting headers capable of achieving the aforementioned header tilt. One tubular component of the assembly is adapted to be detachably mounted onto the throat while the other tubular component of the assembly is adapted to be detachably mounted onto the header, there being a lower pivot between the two components providing the relative rocking therebetween to present the desired tiltability of the header relative to the throat.