Any district which has complied with Section 3A-7 and which is authorized to issue bonds under Sections 3A-6 and 3A-7 shall adopt a resolution specifying the amount of indebtedness to be funded, whether for the purpose of paying claims, or for paying teachers’ orders. The resolution shall set forth the date, denomination, rate of interest and maturities of the bonds, fix all details with respect to the issue and execution thereof, and provide for the levy of a tax sufficient to pay both principal and interest of the bonds as they mature. The bonds shall bear interest at a rate not to exceed the maximum rate authorized by the Bond Authorization Act, as amended at the time of the making of the contract, payable annually or semi-annually, as the board may determine, and mature in not more than 20 years from date thereof.
     With respect to instruments for the payment of money issued under this Section either before, on, or after the effective date of this amendatory Act of 1989, it is and always has been the intention of the General Assembly (i) that the Omnibus Bond Acts are and always have been supplementary grants of power to issue instruments in accordance with the Omnibus Bond Acts, regardless of any provision of this Act that may appear to be or to have been more restrictive than those Acts, (ii) that the provisions of this Section are not a limitation on the supplementary authority granted by the Omnibus Bond Acts, and (iii) that instruments issued under this Section within the supplementary authority granted by the Omnibus Bond Acts are not invalid because of any provision of this Act that may appear to be or to have been more restrictive than those Acts.