Any housing authority shall have the power and authority, after it has undertaken and completed a project whereby it shall have demolished, cleared or removed buildings from a slum area, to lease to the Commonwealth or any of its agencies or instrumentalities of government, including the General State Authority, 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 small be deemed necessary, in and to such slum area, or any part thereof, together with any improvements, buildings or structures therein or thereon, owned 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 so leased, granted, assigned or conveyed 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.