Abstract: A rail brace assembly is adapted to buttress the head of a stock rail selected from one of two different stock rail groups mounted on the top surface of a brace plate. The assembly includes a stop block assembly also is affixed to the brace plate top surface. A rail brace moveable between a first brace position in which it buttresses the head of a rail from a first stock rail group and a second brace position in which it buttresses the head of a rail from a second stock rail group, has a pair of spaced side walls, an upwardly facing top surface, first rail group head and base fishing surface contact areas, second rail group head and base fishing surface contact areas, a first rail group brace plate contact surface and a second rail group brace plate contact surface.