The flat takers have been residing here for thirty seven years. Builder never wanted to construct any more flats because he never applied to the concerned authority for granting additional floor space index (FSI). Therefore, it is a fit case for deemed conveyance.
For deemed conveyance the terms and condition of the agreement duly executed between the builder/promoter and flat buyers shall still applicable. You (flat buyers) cannot ignore the conditions to which agreements for sale were executed. In Tushar Jivram Chauhan v. State of Maharashtra, 2015 SCC OnLine Bom 3865 the Bombay High Court has held that the entitlement of deemed conveyance, even if any, cannot be beyond the agreement between the parties.
It is settled that one cannot transfer any movable and immovable property unless he possesses the right to do so in accordance with law. There are various facets and/or aspects of transfer of property movable and/or immovable.
If, according to the prevailing terms and conditions of the agreement for sale, builder/promoter and his legal heirs still have the power to execute deed of conveyance in the favour of flat buyers, then you can approach the concerned authority under the MOFA Act, to compel the builder’s legal heir to execute conveyance deed.
The Maharashtra Ownership Flats (Regulation of the Promotion of Construction, Sale, Management and Transfer) Rules, 1964, Rule. 13 deals with deemed conveyance. Thus, deemed conveyance is still possible by builder or promoter even after thirty seven years of transferring possession to the flat buyers.
In this situation you should apply to the appropriate authority constituted under the MOFA Act, to issue a deemed conveyance certificate to the flat buyers.