My experience with engine smoke is...if it smokes at the first startup, usually valve guides or seal are bad. The engine oil sits and seeps through these areas and a startup after a wait will suck the oil into the combustion chambers. The engine heats up and expands a little to seal the areas a little better. If your trucks warmed up and you step on gas and it smokes, this would usually be rings. Oil seeps past the rings while running and pushing the motor harder cause pressure to push oil past those rings. Sounds like your motor may need a little help soon, or for a few more miles I think there is some type of oil treatment that can help hold a rebuild off a little longer.