Your facts are not clear. If the plot was in your grand father's name, how could there be a co-op building, unless your grand father had given sub-lease of the plot to the co-op society?
Please have searches made in the local registry regarding leasehold ownership of the plot. In case, your grandfather's name is recorded in the land records, you can certainly apply to BMC for mutating your name submitting the death records of your grandfather and your father.