Photogrammetry based gravestones and tombs for your project,

13 meshes with 3 variations of detail - Highpoly (~80k tris), midpoly ( 4-6 k tris ) and lowpoly with range of 1000 - 2000 triangles.

Meshes have proper roughness, ground-plane baked AO , properly aligned normals and clean, readable UV.

Also textures contain separate 16 bit height maps, which you can use for displacement and additional details.