The sums appropriated pursuant to the first sentence of section 1391 of this title shall be available for grants to States by the Secretary during the fiscal year ending June 30, 1964, and the succeeding fiscal year; and the sums appropriated pursuant to the second sentence of such section for the fiscal year ending June 30, 1966, shall be available for such grants during such year and the next two fiscal years, and sums appropriated pursuant thereto for the fiscal year ending June 30, 1967, shall be available for such grants during such year and the succeeding fiscal year. Any such grant to a State, which shall not exceed 75 per centum of the cost of the planning and related activities involved, may be used by it to determine what action is needed to combat mental retardation in the State and the resources available for this purpose, to develop public awareness of the mental retardation problem and of the need for combating it, to coordinate State and local activities relating to the various aspects of mental retardation and its prevention, treatment, or amelioration, and to plan other activities leading to comprehensive State and community action to combat mental retardation.

Payment of grants under this subchapter may be made (after necessary adjustment on account of previously made underpayments or overpayments) in advance or by way of reimbursement, and in such installments and on such conditions, as the Secretary may determine.