FIFO Costing Method Inventory Part Revaluation

Updating the cost set 2 and copying to cost set 1 will only change the Inventory values of Standard Cost - Cost per Part cost inventory value. If for instance you have added an overhead to a part cost template, you would need to:

1. Calculate costs and copy to Cost set 1 so that the OH is reflected in the Cost set 1 part cost template
2. Now the only way a user can update FIFO cost is to cancel a receipt and re-receive at the new cost.

In an instance, so they purchase 5 units at $10 and then 5 units at $15 and they want to revalue all the stock on hand to say $8 is there any simple way to do this? The only way I can think of is to manually issue all the parts, change the estimated cost and manually receive back into inventory.

Thank you for your questions. Let me explain it further,
NISS and NREC is probably quicker than unreceiving and re-receiving POs, but I have to ask WHY. The point of FIFO is to carry receipt actual cost in inventory, but customer is wanting to do a Standard cost -like function. Should they be using Standard cost instead? If they using FIFO because they don't want any PPV, then they could also use Weighted Average valuation and accomplish the same thing.
From another standpoint, Inventory Valuation for FIFO parts acts like a simple Weighted Average: total inventory value / sum of all quantities in stock. In the example you gave the Inventory valuation would be $7.50/part.
Hope this clarifies your query.