Any portion of the constitutional fuel tax provided for and allocated to the account of each of the several counties by s. 9(c), Art. XII of the State Constitution may be pledged and used for the payment of bonds issued by the division; provided, however, that such funds may only be pledged and used with the consent of the state agency supervising the state road system and the governing body of the county to the account of which such portion of the constitutional fuel tax is allocated.