Unable to update the Basis Type From "Total Value" to "Item" for the existing items for a cost type

Hi We are using FIFO costing method - name given FIFO Rates with multiple org disabled checkbox and basis type as "Total Value"; Now we are trying to change the basis type from "Total Value" to "Item".  For the new items this can be done by making the appropriate changes in the default values; but for the existing items we are unable to do so, because of following reasons:

1. We are unable to see the Cost type created in the LOV of the mass update program as it is not multi org enabled.  When we try to enable the multi org, it is not allowing us to do so as it is defined in other orgs also.  How do we enable the multiorg check box with out errors.