Thank you for your prompt response. No we do not intend to import a catalog. 

Due to the fact that the vendor (manufacturer) is implementing a new software they are  changing the item id 

Example: Item A123 will be 657987.

This are items we carry in our inventory.

What we intend to do is we need to have new item set up, item 657987 and merge it with A123. This way we have the history from prior. If we only bring over the new item and not merge, we will have two items on the list.