From what the guy told me at the IH dealer, those 180*F thermostats were used in school buses with 6.9's.
They sell very little of them. They also had a 160* one!
And mine has been in my motorhome for well over 6 years, not a single problem.... and she gets worked!
I do have a real temp gauge to boot.
I like the sound of a lower thermostat temp will all the coolant issues I had with my crew cab. If you can find a part number for those, that would be great.
Heath