Run the Valuation Change utility in a test company first, and review the impact of this change on all applicable processes.

If there is zero QoH you can technically change the Valuation in Item Maintenance, but watch out for open SO / PO because there is a Valuation column in lines data.  Transaction history should be fine.

Types of Goods and Valuation are two different things in Sage 100.  A item can be a raw material or finished good and can be a lot item.  It is best to use Inventory Transaction to bring in the Lot quantities because it gives you the ability to set cost per lot at this point. If you try Physical Count you cannot assign at cost.

Ah Kevin there is nothing to change if the items are setup as Finished Goods and the Valuation is set to Lot

True, but I was assuming the Valuation is something else currently, which is strongly implied by the original question.

Kevin,  Thank you, that was what I was looking for.  I had not previously delved into that Utility, didn't realize that was the purpose of it.  I knew that I was not able to change the costing method in most cases for existing items through Item Maintenance.  

Thank you