A question about a 2000 Dodge Dakota V6?

Had intermittent oil pressure. Changed oil pump. Truck might run 15 miles with good pressure and suddenly go to zero. And it does loose pressure. You can start to hear the lifters slapping. Turn it off coasting wait maybe three seconds and start again and you got oil pressure again. It might run another mile and after a few seconds or it can be minutes it goes to zero again. Is there anyone else that has had this and can help.