Has the tank ever been replaced? Has the sock on the fuel sending unit ever been replaced? Has the fuel line ever been replaced? What about the rubber lines? Is the in line filter flowing?
Based on what you discribed it sounds like the carb was not getting any gas when it stalled?
I wonder if you have a bunch of debrie in the tank that could be cloging the sock filter? It get stired up and starves the pump? Wait a while and the debrie falls to the bottom of the tank. Just a theory.
I hate messing with fuel problems. I upgraded my fuel system in stages and it would have just been better to do it all at once. I have a new tank with RobbMc pick up. 1/4 return line. 1/2 supply line. Stock fuel pump. This system works well for me.