mreed1, you don't say if this is an engine that's been fine for a long time, and all of a sudden developed this problem or if there were changes made to the engine, and now you've got a problem. One thing I've seen mentioned is that many of the 5.0's were EFI, and when converted to a carb the eccentric is added but the pin in the cam is not changed. The pin for the mechanical fuel pump application is about 3/16" longer to extend out well past the surface of the eccentric. If the shorter pin was left in there it's common for the eccentric to "jump" the pin and cause loss of fuel, and it may "grab" occasionally making it a sporadic problem.