Solid Lifters.
Driving the truck this morning, it ran perfect. Not a single stumble in the 2 miles to work
I agree, that it doesn't really add up, but I think I may have cleaned up a vacuum leak while checking the torque on all the manifold studs, and the carb mounting bolts again. This would follow the 'a vacuum leak that seals itself as the manifold heats up' and is a more reasonable explaination than a valve/lifter problem right now.
bbbbbb2 is any of this familiar enough to be of help? I hate to think we just drove you away. Hope you are making progress as well.