GreetingsCustomerand welcome to JA! I will do my very best to assist you with your problem.
Does it matter if the a/c is on or not?
Ok,I suspect you may have a possible head gasket issue. It may be putting hot exhaust into the coolant and causing the overheat. You should get a combustion test kit and check for exhaust gases in the cooling system.
If you can eliminate this, then you may want to try a water pump.If the pump isn't moving the coolant like it should it will overheat as well. I haven't seen many problems with the water pumps on these because the fins are good and solid,make of steel.So they don't tend to break. This is where I would start. Also, make sure you are getting all of the air pockets out when you refill the coolant. There is a bleeder that must be removed when refilling the coolant. It is located on top of the upper intake and is a ten mm bolt.