William C Allen Tenn & Ark

I was wondering if anyone could help me find info about my greatgrandfather Wiliam C Allen, he was in the Confederate Army in Tenn, He was on the raid with John Morgan at Buffington Island, Ohio [and Ind.] In 1914 or 15 Him and Dudley T Moore were honored for their service at Buffington Island, Ohio, the plaque between them says: "54 years ago, John Morgan made a raid through Ind. Ohio whare with W. C. Allen and D. T. Moore The Blue and Gray met at Buffington Island, Ohio." The plaque is hard to make out, this is the best I can figure with a magnifying glass.
I was wondering if there is anyway I can find William C Allen's pension papers and what he did in the Civil War... I have been searching for years for his pension papers, but everytime it is the wrong file...
Does anyone know what I can do to get the right one?

Thanks
Tanya