Just came in from attempting to fix this. Lifted front of truck a good 2' into the air, ran with cap off, no bubbles. Air temp at outlets in cabin at 105', so some heat is making it to the heater core.

Odd thing, and now I am thinking I have a bum thermostat, is the lower radiator hose NEVER got warm. I did loosen the thermostat housing and coolant came out so I know coolant is there.

Truck is not over heating, though our temps have been in the 40's at the hottest. May attempt draining radiator and putting in new thermostat tomorrow.

I did back flush the heater core and it was clean and flowed well.