Notwithstanding any provisions to the contrary contained in Article 2 (commencing with Section 1770) of Chapter 1 of Part 7 of Division 2 of the Labor Code, the director need not determine the prevailing wage rates before the work under any such contract is commenced. However, such contract shall contain a provision that the contractor shall pay prevailing wages for the crafts or trades so utilized which wage rates shall be ascertained as of the date of such contract by the director as soon thereafter as is reasonably possible.