The portion of United States highway 75 from the northern interchange with United States highway 400, then south to the southern interchange with United States highway 400 is hereby designated as the Pack St Clair highway. The secretary of transportation shall place markers along the highway right-of-way at proper intervals to indicate that the highway is the Pack St Clair highway, except that such signs shall not be placed until the secretary has received sufficient moneys from gifts and donations to reimburse the secretary for the cost of placing such signs and an additional 50% of the initial cost to defray future maintenance or replacement costs of such signs. The secretary of transportation may accept and administer gifts and donations to aid in obtaining and installing suitable signs.