Top U.S. drugmaker Pfizer and Irish rival Allergan are charting independent futures after scrapping a record $160 billion deal torpedoed by new Treasury Department rules meant to block American companies from moving their corporate addresses overseas - on paper - to avoid U.S. taxes. The rules issued Monday, aimed at stopping the companies' "tax inversion" deal, wiped out its financial incentives and rationale for Pfizer Inc., though they had no impact on Allergan PLC.