Did either man or either wife live long enough to fill out a pension application for indigent soldiers and sailors? There is so much helpful information on these pension forms -- about their dates of birth, marriage, where they live, who they have in their family. You might be able to identify your man that way. The pension was applied for in the state the soldier lived in, not necessarily where he enlisted or served. The Mississippi and Louisiana pensions began about 1890. Check familysearch.org and look under "United States" to get started. You won't believe the help you will find there. (No, I don't work for them!)