I cannot help you locate your GGGrandfathers' grave, but found your request of interest. My GG Grandfather fought there also - but as a Union soldier with the 39th Iowa Infantry. He was captured at Alatoona, but managed to escape 2 months later. His name was Hiram Potter Sherard.
I also have a GGrandfather who found as a confederate (29th Virginia Infantry). He commanded company C and was present at Appomattox for the surrender.
Best of luck in your search for your GG Grandfather's grave.