99 Mercury Villager still overheating!

You replaced all that -- including head gaskets -- assuming both banks? What testing was done to condemn them? It's not a usual failure on this Nissan engine. I don't see the water pump being a concern unless you had some crazy vehicle corrosion in the cooling system that could have damaged it. I'd purge air pockets out of the cooling system to see if maybe air is trapped, then seek the help of a shop near you. www.repairpal.com/repair-shops