Overheating issues

I recently had the motor rebuilt. And it started overheating. Replaced the thermo and pump did a flush and it is still over heating. I know there is probably a post somewhere on here but it is pretty urgent considering it is my only means of transportation. Any ideas of what the issue could be

 

air in the system. backwards thermostat. backwards head gaskets. not a 50/50 mix of coolant/water.

 

What caused the Engine to fail in the first place ??

What shape is the radiator in full of dirt

Who did the engine ??

 

Thanks for the response.

Threw 2 valves in number 6 cylinder. Replaced the heads and valves. A Toyota mechanic did the rebuild.
I'm going to drain the radiator again and look to if the core is clogged up.

 

Make sure the fan is running

 

I did a complete rebuild at 197k miles. I had 3 different t-stats that were causing the truck to run very hot after a rebuild. Went to a Toyota OEM t-stat and it runs much better. Does it overheat when driving or only when idling? If idling, I would check the fan clutch. The radiator may very well be clogged and not allowing sufficient flow.

Radiator - lower hose - t-stat - water pump - upper hose. It has to be one of those if the Head Gasket is good.