If the body had a body tag plate on the firewall, it generally would have been located on the right side of the cowl above the battery box. Look for two small holes indicating where the tag was located. No holes or indentations for same would indicate that the body is Ford built, not an out-sourced unit.
Generally speaking, though the years I have found that Ford did not like/let his vendors brand their parts, the exception being Dodge Brothers (DB) on early Model T's. Other manufactures let Briggs, Murray, etc., brand their parts.