2012 GMC Sierra 1500. Installed this radiator with a new Jasper motor with DOD delete.
Works great - almost too well.
At the end of the 12 minute warm-up cycle, truck would show "Engine Hot A/C Turned Off", Cooling fans would come on, Thermostat guage in the dash would drop to the left pin, and P0128 (Coolant Temperature Below Thermostat Regulating Temperature) would go into the pending codes status.
Clearing the code it would all return to normal.
After 4x OE 187* thermostats (3x AC Delco and 1x Murray), I put in a Calorstat 196* thermostat and now the truck hits operating temperature in 1/4 the time and holds 210* perfectly. Rockauto shows this thermostat (part number TH153891) as a replacement for the 5.3L but it is a 2.1" flange diameter not the OE 2.2" flange diameter. So far it appears to be holding with no leaks from the housing and temps all look good.