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, a 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. An elastic fastener cooperates with a clip housing to clamp the rail brace against the stock rail. When the rail brace is in the first brace position the first rail group head and base fishing surface contact areas engage the rail head and base fishing surface areas, the first rail group brace plate contact surface contacts the brace plate and the second rail group head fishing surface contact area engages the stop block assembly. When the rail brace is in the second brace position the second rail group head and base fishing surface contact areas engage the head and base fishing surfaces of the stock rail, the second rail group brace plate contact surface contacts the brace plate and the first rail group head fishing surface contact area engages the stop block assembly.