White smoke and slapping noise

I will start off with background. Got oil changed, checked level its good, next day truck started running rough when cool, about a day later coolant was low and white smoke started showing up while the engine is cool (I live in TX and its still hot so this is not the normal from air temp). I have replaced the spark plugs and added coolant. After replacing the plugs the truck ran good at start up for a day then went back to normal. The day the truck overheated I added coolant (I had forgot about it the few days before, and level showed low but not out) The next day the truck had a slapping noise coming from under the hood when I started it. I have not drove or allowed the truck to run since then. I have been told the smoke was the heads needing to be replaced but what about the slapping noise and is the heades advice correct? Sorry this is so long guys but I know the more info the better. I have about 90K on this 4.7 2004 dodge ram.