According to the 1890 veterans census, a James Ballayer or James Ballinger served in company B of the 91st, from 3 April to 13 July 1865 (PA, Philadelphia, Philadelphia, supervisor's district 1, enumeration district 355, page 2, line 17 [image 760 on <www.ancestry.com>]). James Dell is the closest match I have found.
He was 20 years old when he was enrolled (2).
He was a substitute (1, 2). He was enrolled and mustered into service on 24 March 1865 (1, 2). He was enrolled at Chambersburg, Pennsylvania (2). He was mustered in as a private, at Chambersburg, Pennsylvania (2). He served as a private in company B (1).
He was absent, sick, when the regiment mustered out (1, 2).
1 Bates, Samuel Penniman. History of Pennsylvania volunteers, 1861-5. Harrisburg: B. Singerly, state printer, 1869-71. 5 volumes. 'Ninety-first regiment', volume 3, pages 186-233. (In the roster) (James B Dell)
2 Civil War Veterans' Card File, available at the Pennsylvania State Archives, searched 28 June 2004 (James B Dell)
[I did not find an entry for him in the index on <www.ancestry.com> to the pension index by name (searched December 2006)