The provision of this Section shall apply to all developments, enlargements, extensions or alterations. All existing buildings within the Preservation Area shall be considered complying buildings for all purposes including, but not limited to, alterations, enlargements, extensions or conversions to residential uses. Any existing building which is damaged or destroyed by any means may be reconstructed to its bulk prior to such damage or destruction. All existing legal uses in enclosed buildings shall be considered conforming uses. Except as otherwise provided in this Chapter, any existing commercial or manufacturing uses may be changed, subject to the applicable underlying district regulations, pursuant to the change of non-conforming use provisions of Sections 52-31, 52-33, 52-34, 52-35 and 52-36.