Replaced the thermostat, and outlet pipe. No more bubbles, truck heats up to operating temp but doesn't overheat. Heat works fine. Combustion test still necessary?

 

I would just keep an eye on it and see what happens

 

That's good news. I feared the worst but it appears that air was being sucked into the system from the outlet pipe. As the car warms up it creates a vacuum in the cooling system and is supposed to suck in coolant from the reservoir. With the hole in the outlet it sucked in air because it's easier. When the engine is hot it will squirt coolant out the hole instead of putting coolant back into the reservoir. You shouldn't need the combustion test unless you notice more foaming. Keep an eye on the recovery tank and the coolant level. When cool there should be liquid right up to the top of the radiator when you remove the cap.

 

No issues for the past few days. Had a scare when the truck was leaking copious amounts of liquid but it was just the condensor sweating. Will post pics of my ride in a day or two. Thanks for all the advice folks.