Land mutation

A gifted verbally a piece of agricultural land to B more than 40 years ago. B did not get it mutated. B expired. Legal heir of B transferred the land to C through a deed. C is not allowed to get the land mutated in his name due to absence of conveyance deed between A and B. Sons and daughters of A expired. Grand children are scattered in various corners of India, none is staying in their native land, impossible to contact them. C is in possession of the land. Pls advise the way out. How C can get the same mutated in his name ?