Any housing authority shall have the power and authority, either before it undertakes a project whereby it shall demolish, clear or remove buildings from a slum area, or after it has undertaken and completed such slum clearance project, to enter into contracts with the Commonwealth of Pennsylvania, or any agency thereof, or instrumentalities of government, including the General State Authority, to lease to the Commonwealth or such agency, for a term not to exceed ninety-nine years, or to grant, assign or convey either the fee or such right, title, interest or easement as shall be deemed necessary, in and to such slum area, or any part thereof, when or as cleared, together with any improvements, buildings or structures therein or thereon, owned or about to be acquired by such housing authority, needed by or convenient to the Commonwealth, or any agency thereof, or instrumentality of government, including the General State Authority, for any public purpose or purposes, including the creation of public parks and the erection on the lands contracted for of buildings, improvements and structures deemed necessary for the use of the Commonwealth, or needed or convenient for the corporate purposes of such agency or instrumentality of government.