If you need to display 3D letters as models… like statues with collision or something, then do something similar to what blender3D does (create text object, convert text to mesh (vertice), extrude to 3D).
If you simply wish to display text on top of a tombstone you don’t have to make 3D models at all since you can just use a shader.
In both cases I’d not go for custom made 3D model letters… I’d pick a font compatible with as many languages as I need and use the font data in my shader somehow to offset or color letters on top of a stone.