The way I’ve been doing it lately is to export both the face mesh and body to blender, then use the skeleton of the body for the face and then import the face mesh with the new skeleton from the body back in to unreal, I’ve been using the Mesh Bake plug-in to merge the two meshes. You will need to correct the weights for the head in blender though on the head bone as the front portion of the face was weighted for the. The Mesh Bake plug-in is paid for but you can also just combine the meshes in blender.