I have had tremendous success with off-camera wireless flash. By directing the light across the face of the tombstone you can render worn engraving suddenly visible. The writing and carving is cast in stark relief. An external flash is usually bright enough to overcome the sun, so you can take great photos any time of day. I would be happy to talk to anyone who wants to try this.
P.S. My previous post on this topic was deleted for reasons unknown to me. If you think this is off-topic, or needs to be deleted, please contact me!