If the state of Missouri designates a portion of interstate highway 70 as the Truman/Eisenhower Presidential highway, or something substantially similar, then the portion of interstate highway 70 from the Missouri state line to the junction with highway K-15 shall be designated the Eisenhower/Truman Presidential highway. The secretary of transportation shall place signs along the highway right-of-way at proper intervals to indicate that the highway is the Eisenhower/Truman Presidential 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 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.