Wow, this morning was amazing having heat sooner. Was 37 degrees ambient leaving the house at 0620. Highway travel this morning the truck ran 206 degrees similarly to yesterday.
Called our 2 local dealers and they dont have the thermostat on the shelf, would take a day or 2 to receive from initial order. From what I can find this thermostat was used basically 1999 through 2010, so assuming being so old its not something they mess with on the regular anymore. I scoured several local parts suppliers including AutoZone, Advance, O'Reilly, Carquest and finally NAPA. Our main location actually has the AC Delco part in stock for $34. Fingers crossed.
I did rince the general petcock area on the radiator as for now my plan is to reuse the coolant. Today is going to be nearly 70 degrees so I want to get this swapped today. Tonight we drop into the 20's and only reach 40 tomorrow.