Matt, do the 180 (in the housing right under where the upper rad hose enters the lower manifold......on the fat end of the sc) AND add a tranny cooler. The trans fluid will enter the radiator cooler, and help keep coolant temps down, as well as help your trans live a fuller life.

Check my sig....I'm running dual tranny coolers now. Can't remember for sure, but I think it bought me 5 or 10 degrees of 'cool'.

You may have other issues.....your radiator core may be suffering from buildup, or your water pump may be going south. I'd get that sucker flushed after you change the Tstat. Get the housing gasket and tstat seal from the dealer, and the stat from any auto parts dealer. They'll have to cross-reference for one that will fit.