I have a Mazda B2000 that over heats I changed out the thermostat yesterday and water pump about six months ago it still keeps overheating the water spills out of the over flow as if the thermostat is not opening can anyone troubleshoot with me?

Have you checked for any valves in the system to release air pockets? Did you follow the factory recommended method for changing / adding new fluid?

Possibly a clogged radiator, is it a regular fan that is powered by the drive belts spinning or is it a electric fan?

Make sure your fan clutch is working, check for cloged radiator, and make sure your radiator cap is holding pressure.