overheating problem

ok, so my mom has a sunfire and while changing spark plugs one snaped off in the block, so we replace the head. now it's overheating and we have already replaced the following:
1. radiator
2. hoses
3. water pump
4. thermostat
5. temp sensor
what else is their to replace?

Fluid, Make sure that your coolant is getting to the proper places.
Belt, Check the belt, it may have wiggled loose enough to slow your pump.
Fan, Make sure the fan is working properly.