TVFool.com would be my choice, although now that the DTV transition is history they are updating their database much less often. Their last update was May 22, but that did include KTFO-CD.
TVFool's coverage maps are a little different than the FCC's were: rather than a bright "edge" they show the signal strength via a color-coded map. But it looks like Lockhart has good signal strength from KTFO.