I was able to get quite a bit completed last night but not finished. I think I spent too much time cleaning things and chasing what I thought was a coolant leak.
My plan all along being this deep into the repair would be to replace the thermostats while the cooling system was drained and open. I nearly forgot but fortunately saw the new GM thermostats sitting on the workbench near the FASS system and I remembered. Only had to move a couple of wire looms and removed two brackets and the t-stat housing lifted right up allowing easy access to the thermostats for replacement.
I had one showing it was partially open which makes sense as the last couple of times I drove the truck it struggled coming up to temp and under normal driving sat a bit lower on the temperature gauge than normal so I'm glad I took the time to replace the t-stats.
After cleaning the housing and mounting surface I reinstalled the t-stats and torqued the housing to 15 ft/lbs.
Next I pulled a vacuum on the system to ensure there were no leaks. I generally attach my Air Lift vacuum assembly, pull a vacuum and walk away for 20+ minutes to make sure it holds a vacuum. I wanted to check the cooling system integrity before buttoning up the top of the engine in case I had a leak. Seeing as how I had the lower radiator hose, thermostat housing as well as both coolant hoses going to the turbo disconnected at some point during this repair I wanted to make absolutely certain I had no leaks. Well, things weren't cooperating otherwise I think I could have finished the truck up last night.
I connected the Air Lift to the reservoir, pinched off the overflow hose from the surge tank and pulled the vacuum. It pulled down to around 23 inches pretty well but when I valved it off the gauge started creeping back toward zero. Damnit. I turned the radio off so I could listen and unfortunately heard something else that wasn't so great. I could hear air but it wasn't coming from around the truck and was very faint. After ******* around I decided to walk to the RV storage bay and I could hear my shop air compressor still hissing out the unloaded valve. ****! I've got a check valve with something stuck in the disc or under the spring again.

I figured I'd address that once I get the truck completed but it bugged the ever living **** out of me the rest of the night.
I then went back to the truck to see where my leak was. I could detect nothing. I removed the vacuum assembly and installed my pressure tester and figured maybe I'd have better results using soapy water and pressure in the cooling system. I sprayed around all of the connections that I had disturbed during the repair and found NO BUBBLES. I thought for a moment maybe the overflow tube coming off the surge tank could be the culprit so I removed the hose and installed a rubber cap and worm clamp. It held 14 PSI of pressure perfectly. Well, that must have been the issue.
I removed the pressure tester and reinstalled the Air Lift vacuum assembly, pulled a vacuum down to nearly 25 inches of vacuum, valved it off and walked away for a few minutes. It appeared to be holding perfectly so I resumed the reassembly process. I only wasted about an hour chasing a leak that didn't exist. Oh well, I felt better knowing it was being buttoned up without the possibility of a coolant leak after the truck was up and running. That is why I love using the Air Lift so much as there is no guessing and no relying on luck not to have a leak. With as many cooling system connections and hoses on the modern automobile there are just too many possible leaks to leave them to chance.
Reattaching the upper coolant hose brackets to the rigid line as well as reconnected the turbo vane sensor connector.
I fixed the small 1/8" line that feeds my boost gauge on my A-pillar and connected my Kent Moore intercooler tester to ensure there were no leaks to the intercooler assembly or piping. All looked good as far as intercooler integrity.
This picture is for WoodsTruck. I didn't end up having to apply any additional anti-seize as there was already a light film on the battery hold down bolts from previous removal/installation cycles. This is my general use anti-seize that gets used for such things as this that aren't prone to high heat. I also use this on all suspension components as it has excellent staying properties, even on our Utah winter roads.
Thanks for looking.