If you want to change the name in Pan Card as well as in Income tax Filing, you firstly need to fill up the form Application for Request for New PAN Card Or/ And Changes Or Correction in PAN Data (PAN Change Request Form) available at online also. But you must enclose proof for the same name. After change the name in Pan Card, intimate it to Income tax department, that the pan card now contain the changed name.
If there is no proof for your father's name Ram Ganediwala , then you have to complete the change name proceeding. For this you have to file affidavit and notice of change of name into two local daily papers i.e. one in local lnguage and 2nd in english daily. Thenafter your change name published in official gazette. The copy of this gazette enclosed with PAN application. Name of your father will be change.
Correction of PAN will serve your purpose and it may be done through any one agency. They will guide you. I believe that they may require you to produce any proof for the present name, otherwise to produce letter from a gazetted officer. They will give you the format.