Contracts for the construction of state aid road projects shall be advertised and let by the board of supervisors of any county desiring so to do, in the manner now required by law but subject to the approval of the State Aid Engineer; however, during the last six months of the boards of supervisors' terms of office, no contracts for state aid projects shall be awarded unless construction programs embracing such projects shall have been adopted by the boards and approved by the State Aid Engineer in writing prior to July 1 of said year. Before advertising for bids, detailed plans and specifications covering the work proposed to be done shall be prepared and filed in the chancery clerk's office of the interested county and in the office of the State Aid Engineer; and copies shall be subject to inspection by any party during all office hours, and shall be made available to all prospective bidders upon such reasonable terms and conditions as may be required by the State Aid Engineer. All plans and specifications shall be initially prepared by the county engineer, subject to the approval or disapproval of the State Aid Engineer. All rights of way necessary for such projects shall be acquired and paid for by the boards of supervisors in the manner now provided by law for the acquisition of rights of way, including gift, purchase, deed, dedication, and eminent domain; however, the cost of such rights of way shall not be considered to be a part of the cost of any project within the meaning of Section 65-9-17. The acts of the boards of supervisors in heretofore acquiring rights of way for such projects, and all rights of way heretofore acquired for such projects are hereby ratified, confirmed, and validated.