Sliding Support Material at 970ºF

He have a Main Steam Line that work at 970 ºF, The flexibility analysis establish the transversal load near 3000 lb and vertical load near 4000 lb, what is the material more conservative to use in sliding support?. We considered that use A36 is not appropriated to effort at 970 ºF, could be used A287 but it give a short range of work, and use A387 that is bigger range but it’s very expensive.