Thank you very much. No idea how I didn't find this before, I searched for hours. Still have some learning to do I guess. Parts ordered.2261256350 - plate (~$23)
2219364750 - O-ring (~$3)
This is for a pre-92 HDJ81.
See this thread for more info: ACSD - Blanking plate part number - https://forum.ih8mud.com/threads/acsd-blanking-plate-part-number.634271/page-3#post-13622508