The notion that Winn Parish actually seceded from the State of Louisiana is just story telling. At least half of the population was pro-Confederate during the war. Most of the other folks were anti-war and only a few were out and out Unionists. There were a surprisingly large number of slave holders in the parish, although there were only one or two large plantations along the Red River.
The West and Kimbrell Clan was real, although the actual story is shrouded in myth and legend. Never heard of Jessie and Frank James being part of the story. Richard Briley, III wrote "Nightriders: Inside Story of the West and Kimbrell Clan" which he self-published at Montgomery, Louisiana in 1962. On the cover is the advertising teaser "John West and Laws Kimbrell - Greater Than Frank and Jessie James" - maybe this is how the James connection was erroneously made. The original was a paperback, but maybe your local library could lay hands on a copy.
Laws KIMBALL of West Clan fame served in Company D, 12th Louisiana Infantry and was 2nd Sergeant of Companies A & D at the surrender in North Carolina in 1865. The hero of Briley's account was Daniel C. DEAN who served as a Private in Company D and was also present at the surrender in North Carolina in 1865. Laws and Dan came home from the war together.
Company D was recruited from the communities surrounding Montgomery which was part of Winn Parish before Radical Reconstruction created Grant Parish out of Winn and Rapides. The family name is spelled many different ways: Kimbrill, Kimbrell, Kimball, Kimbell, etc. Two other KIMBALLs served in Company C (also Winn Parish) in the 12th Louisiana, and there was a KIMBELL in one of the Claiborne Parish companies.
Once upon a time, I went through Briley's book and identified all of the Winn Parish Confederate veterans involved - on both sides of the law in this case.