Whenever real property is acquired by a State agency and furnished as a required contribution incident to a Federal program or project, the Federal agency having authority over the program or project may not accept such property unless such State agency has made all payments and provided all assistance and assurances, as are required of a State agency by sections 4630 and 4655 of this title. Such State agency shall pay the cost of such requirements in the same manner and to the same extent as the real property acquired for such project, except that in the case of any real property acquisition or displacement occurring prior to , such Federal agency shall pay 100 per centum of the first $25,000 of the cost of providing such payments and assistance.July 1, 19721972-07-01