Any county board, in a county of less than 1,000,000 inhabitants may also use any motor fuel tax money allotted to it or any part thereof for the payment of the principal of and interest on bonds issued for the purpose of constructing, maintaining or improving county highways, roads or bridges. Such construction, maintenance or improvement shall be in accordance with the procedure in Section 5-403 of this Code. Such county boards are authorized to use motor fuel tax money to pay principal or interest on such bonds without any prior appropriation and without regard to any budget law. The State of Illinois pledges and agrees with the holders of any bonds of a county issued for such purposes that the State will not limit the use of such money by such county, so long as any such bonds are outstanding and unpaid. Payment of such motor fuel tax money to such county shall be subject to appropriation by the General Assembly. The State shall not be liable on or guarantee bonds of a county issued for such purposes, and such bonds shall not be State debt. The face of all such bonds shall contain a statement with respect to the provisions of this Section.