If you are using ASTM specification A 312 "Standard Specification for Seamless and Welded Austenitic Stainless Steel Pipes" for high temperature service, there is no 317H grade. Use 317.
Have not seen anything yet. The 317 has a 0.08 carbon max limit and most likely would have similar strength and creep properties to an H grade if the material was purchased to the max carbon limit.