Jim,
I don't know of any other sources, being a neophyte family historian/writer, but would welcome any other information I could get. My research on my John W. Powell of Clark's regiment has him at Ft. Pleasants in April, then nothing more. He either died at Ft. Pleasants or on the expedition, because he disappears and is not present on the rosters of the 9th MO. Von Phul's after action report gives some scant information regarding the damage to a gun carriage, etc., but no reports of who was killed or anything. I haven't found an after action report by Musser, so don't know if he gave more info or not. I would welcome any further information on Clark's regiment during 1863.
Ray Walters
Independence, MO