Run it with the t-stat removed. If it is still having the same issue of overheating and pushing coolant, then start checking plugs and leak down rate.
There is another reason for running it with the T-stat removed. When it is removed and you run the engine with the radiator cap off, you should see the coolant flowing smoothly in your radiator (hopefully you can with your truck as I'm not sure where the pressure cap is in that system.) If the coolant is NOT flowing smoothly, then you have an issue with blockage or water pump. If the coolant flow smoothly but bubbles begin to develop and continue to get worse as the engine warms, then head or headgasket is most likely the cause.
"i had the cap removed, and then turned off the engine. Also a note to add is the coolant is surging at a rate that makes it impossible to fill while running. At the rate it is surging it would push all of the fluid out of the system if i allowed it to. "
You are describing a cooling system blockage to me, a plugged radiator or a thermostat installed upside down or one that is will not open completely. That also happpens when the coolant is extremely hot. Does the surging issue you have when trying to add coolant occur when you 1st start it or when trying to add coolant with it running and engine hot?
Did you install a new water pump or radiator when you put the motor in? And what happenned to the original motor?