All lands purchased from funds heretofore allocated and made available by Executive order, or otherwise, for the acquisition of lands for conservation or forestation purposes within the maximum boundaries of the Isle Royale National Park, as authorized by sections 408 to 408b of this title, are made a part of the said park as fully as if originally acquired for that purpose and the proviso at the end of section 408 of this title shall not be construed so as to prohibit the acquisition of lands in the park area with the aforesaid funds.