I don't know a regimental history that has been published, but a book of interest would be the diary of Captain Ethan Allen Pinnell of Company D was published a few years ago as "Serving With Honor: The Diary of Captain Ethan Allen Pinnell of the Eighth Missouri Infantry (Confederate). Published by Camp Pope Bookshop and edited Michael E. Banasik.

They were not at Helena...they were at Fort Pleasant at/near Pine Bluff. They were at Prairie Grove.