If your father wishes to make you a proprietor of the firm then he need to execute a gift deed whereby he is transferring all the business of the firm alongwith its assets and liabilities in your name.
This way he could make you the proprietor during his lifetime and no one can challange the same.
Further, you would also have to initimate the court about the same by filing an application before the court alongwith the copy of the registered gift deed. so that your father's name could be replaced with yours as a proprietor.
Advocate Rohit Dalmia