I just noticed a listing for an "Overton Family Cemetery" on the Shelby County Algenweb site. (www.rootsweb.com/~alshelby/shelby.html ) It is described as being SW of Vandiver on Highway #43. Turn on unpaved road across from Pleasant Valley Baptist Church and take the left fork to the cemetery. This should put it in the vicinity of Penitentiary Mountain. Unfortunately it is described as being overgrown and with no grave markers. The number of graves was unknown. There were no names for those buried there only the name Overton Cemetery.
I just thought that since it seemed to be in the area of your search you may like to known about it. Maybe you can visit it when you come. I have some Overtons with distant family connections. I guess I need to check up on my on research. Maybe there is a connection. If you get down here letme know an maybe we can search together. Ron