You're misunderstanding what the T-stat does.
It's a device to keep the temp at the optimal level, namely at the spec on the T-stat. Any colder and it closes, any warmer and you don't have enough cooling capacity and your system is marginal.
If you had a fan shroud and a stock T-stat, it should quickly warm up and then stay at the temp of the T-stat. The stock temp gauge is as good as an idiot light. Once it moves up to the danger zone it's already WAY overheating.
A lower temp T-stat on a properly functioning cooling system will lower the temps to the T-stat's level, but at 180 it's too cold.
To the people that mentioned it, this is the same exact radiator as the Haste. Much like the cheap chinese coilovers, they will stamp whatever name you want on it, but it's the same exact product.