Please forgive this intrusion into your discussion to clarify that the Old Fort Laramie Post Cemetery is several hours away from the large, modern city of Laramie, Wyoming. No, the old post cemetery is part of Fort Laramie National Historical Site near the village of Fort Laramie in east-central Wyoming off US Hwy 26 between the villages of Lingle and Guernsey, Wyoming. The question you face now is did Colonel Shanks die and was buried in the city of Laramie or at the old Fort Laramie post cemetery many miles away?
The old fort itself is under the jurisdiction and care of the National Park Service (NPS), and the old post cemetery is also on the grounds of this federal site. Just in case this is pertinent, the village of Fort Laramie cemetery is nearby, contains graves old and new, and it is not part of the NPS site. If you contact the NPS personnel at the old fort, they may be able to give you information regarding Colonel Shanks burial, since part of their mission is historical interpretation of aspects of the old fort to the public. They do have a small permanent staff during the off season. Colonel Shanks may have been traveling somewhere at the time of his demise, since several notable pioneer trails passed by the old fort, or he may have died at the city of Laramie, which was a major transportation stop by 1870.
However, you may want to clarify his precise place of death and burial. It's possible that the VA provided an appropriate Confederate tombstone, if it was requested, or survivors may have provided a private stone. The Wyoming State Archives, Research Division, last I heard was in the Barrett State Office Bldg 2301 Central Ave. Cheyenne, WY 82002 at phone (307) 777-7826.
Some years ago I worked a summer as a seasonal ranger at the site, and had occasion to visit cemeteries near the old fort. I also drove the long trip to Laramie once or twice on my days off.
I hope this helps. Bruce, I benefit very much from your wonderful "Confederate Colonels" book in my own research and writing, and I am happy to cite the book.