180 or 190 thermostat?

For what it is worth, I don't run a thermostat on mine. I have different pulley's to slow the water down and a big cross flow aluminum radiator with an 8 blade PRW mechanical water pump, Fiscous fan & NO Shroud along with a 29PSI Cap. Mine runs 175* most all of the time no matter how hard I beat on it. I did see it Creep to about 195*-200* last summer in stop and go traffic. Mine works well as is and I run it hard. As said if it works the way you have it...... leave it alone. Mine is a 410 Stroker, Solid Cam, Iron Heads & on a 180 NOS hit to boot.