As per the scenario you have mentioned, the best way to transfer the ownership is via gift.
A gift deed is a document that transfers property to another owner as a gift. A Gift Deed is valid only when it is without any consideration. According to Section 17 of the Registration Act, 1908, it is mandatory to register Gift Deed.
The transfer of house property as a Gift has to be backed by a registered instrument or document. It is to be signed by your father, attested by at least two eyewitnesses.
A gift deed must also be registered in the sub-registrar’s office. The registrar will ensure that proper stamp duty has been affixed on the gift deed when it is presented for registration. As soon as the gift deed is registered, your father will lose his ownership over the gifted house.
Hope it helps,