Any help is greatly appreciated, I am at my wits end with this truck!

Model # GP030BDJUAV079
Serial # N459727

My D5 gas motor w/carb Starts when turning the key, and it feels like it looses spark as soon as it starts and I let off the key.
I have confirmed I have spark at all 4 cylinders and I have confirmed I have fuel flow and a full carb bowl.
New Parts:
Ignition switch
Cap
Rotor
Ignition Module
Plug wires and plugs (order confirmed twice)
Rebuilt carb
Fuel filter (installed additional inline glass filter to verify flow and tank condition)

While hunting down a no spark condition, I have confirmed there is 11+ volts at either side of the coil and a blue spark coming off of all of the plugs.
I pulled the vac. line off of the pneumatic governor valve, I have confirmed before and after cranking the governor butterfly is still open.