The provisions of sections 35 to 45 of this title shall not be construed to modify or amend Title III of the act entitled ''An Act making appropriations for the Treasury and Post Office Departments for the fiscal year ending June 30, 1934, and for other purposes'', approved May 3, 1933 (commonly known as the Buy American Act) (41 U.S.C. 10a et seq.), nor shall the provisions of sections 35 to 45 of this title be construed to modify or amend the Act entitled ''An Act relating to the rate of wages for laborers and mechanics employed on public buildings of the United States and the District of Columbia by contractors and subcontractors, and for other purposes'', approved March 3, 1931 (commonly known as the Bacon-Davis Act), as amended from time to time (40 U.S.C. 276a et seq.), nor the labor provisions of Title II of the National Industrial Recovery Act, approved June 16, 1933, as extended, or of section 7 of the Emergency Relief Appropriation Act, approved April 8, 1935; nor shall the provisions of sections 35 to 45 of this title be construed to modify or amend chapter 307 and section 4162 ^[1] of title 18.