Overheating on run stand

So no thermostat yielded no overheat and adding a 180 degree thermostat yielded overheating. That kind of points towards a faulty thermostat. I would recommend doing a few things.
1. Take out the thermostat.
2. Test the thermostat in a pan of water. It should "start" to open at 180 degrees.
3. Try to check for an airlock and drill a small hole in the thermostat like @George Jets suggested.
4. Run the engine without the thermostat and see if it overheats. If it doesn't, I'd try another thermostat.
5. If it does overheat, let it cool down completely and then:
a. Take the radiator cap off and start the engine. If the water pump is working properly, you should see water flowing
through the radiator. If not, maybe you need a new/better water pump.
b. Try playing with the timing.
c. Is the electric fan on the radiator big enough?
d. Was the block properly cleaned out in the water passages? You know what blockage there would do! Maybe a
thorough flushing of the block and heads would be in order.
That's about all I can think of. Good luck, Steve.