Is there a way to manually add a purchase order to a new sales order line for a drop ship?

We have 90+ drop ship sales order lines with an associated purchase order where we need to cancel the sales order lines in order to update a master item attribute (can't do this with open sales order lines). Once the master item attributes are changed, we will create the new drop ship sales order lines, then we want to reassociate those existing purchase orders to those new sales order lines.

Does anyone know if this is possible?