David,
After checking my files on Louis Carriere of the 8th La., I'm sure that is not yours as his parents are different also. Here is what I have on that Louis Carriere:
Carriere, Louis, Private

Louis Carriere was born July 3rd, 1832 in Opelousas, LA to Joseph Michel Carriere and Emeline Coulon Devillier. Louis was the brother of Francois Carriere of the same Company. He enlisted at Camp Moore on June 23rd, 1861. Louis was sick often and even reported as absent without leave in the Cavalry from Sept. 1862 to Sept. 1863. Louis transferred to the Confederate Navy in August 1864. Evidently he was a prisoner in Libby Prison in Richmond on April 10th, 1865 and labeled as a deserter. He was denied a pension after the war on those grounds. He married Marie Melina Rattel in Opelousas on May 15th, 1866. Louis farmed in the Prairie Basin. He died of heart disease in Notleyville, LA on Feb. 20th, 1874 and is buried in the Catholic Cemetery in Opelousas. Another record states that he died Feb. 6th, 1878 on Bayou Teche.

Also, this extra date of death somewhat matches yours in that it was the 6th of the month and in 1878. Seems we have some crossed and confusing information here. There is a book out that has the listings of all persons buried in the Catholic Cemetery in Opelousas. That may be worth a look.
Wayne