Turns out that I had blockage in my heater core. Once I flushed the core out I started to get heat in the cab. I also found that I needed to re-adjust the heater valve cable to make sure the valve opens all the way. I removed the little spring that comes with the heater valve. This spring actually worked against me in allowing the valve to open all the way.

I also observed that there is very little warm/hot water circulation in the heater core when the valve is open and the truck is only idling. The real heating comes when the RPM's of the truck are higher than idle.

I've posted a video of the heater core water flow for others to see.

https://swenracer.smugmug.com/Trucks/59-Apache/i-x9nTMRn/A

Scott.