Hello - Is it possible to change item types and not lose historical data? For example, change Inventory Items to a Kit/Package or other types and transfer sales data for that item...

Not that I know of. In fact, some items can’t be converted. You might need to change the original item sku to include “-OLD-“, inactivate it, then recreate the item. The OLD version will retain sales data.

@Michael McNamara yeah, that's what I thought. They want to keep the data within the same item

I think if the item is inactivated, you might not get reporting data. Try both ways and see.