Is it considered forbidden or a bequest to an heir to take gold that my father, may Allah have mercy on him, said during his lifetime was mine, but he did not hand it over to me?

Gold is a right for all heirs and is to be divided among them according to the legal Islamic distribution of inheritance. It is not exclusively yours, whether your father intended it as a gift or a bequest. The gift was not completed by your taking possession of it or by witnessing it, and a bequest to an heir is forbidden by Islamic law unless the other heirs consent.