Enabling Item Cost Flag for Existing Items

Hi,

We have a requirement from Customer to update the Item Cost Enabled Flag to 'Yes', without losing their Item Transaction Histories. Currently they are using FIFO as their costing type, and all items are defined as Expense Item (Inventory & Transactable - but not costable).

Almost all Items have On-hand.

Can anyone suggest me, which would be the better approach to update the Item Cost Flag for all these items - without creating a new one.

Thank you very much in advance