The regulations of this subpart, in addition to the regulations of the other applicable subparts of this part, are applicable to grants under section 330 of the Act for project costs which include the cost of acquisition and/or modernization of existing buildings (including the cost of amortizing the principal of, and paying the interest on, loans), except that, these regulations are not applicable to grants for project costs which include the costs of modernization of existing buildings if those costs can otherwise be supported under subparts B, C, or D of this part.