In case of conflicting claims upon coal lands where the improvements shall be commenced, after the third day of March, 1873, priority of possession and improvement, followed by proper filing and continued good faith, shall determine the preference right to purchase. And also where improvements have already been made prior to the third day of March, 1873, division of the land claimed may be made by legal subdivisions, to include, as near as may be, the valuable improvements of the respective parties. The Director of the Bureau of Land Management is authorized to issue all needful rules and regulations for carrying into effect the provisions of this section and sections 71 to 74 of this title.