Well after taking the heater core to 3 shops to be repaired or re-cored I finally found a shop who was actually willing to look at the core I brought in. The shop owner pressure tested the core and determined that it was a blown seam in the upper tank. The owner removed both tanks dipped the core and soldered the whole thing back together and when finished pressure tested to 15 psi for 45 min with no leaks. The entire service cost me $65 shop time. Too bad the other 2 shops were so unwilling to even have a look. I am pleased with the results and will be installing the core back in the truck first chance I get so Jessica won't have to dress like an Eskimo to drive to school.
Thanks again to everyone who contributed your time is greatly appreciated.

Jessica's Truck

The true definition of insanity:
To do the same thing the same way repeatedly and expect a different result each time.