Jeff,
A diesel of this age shouldn't blow any smoke when started, but I work with one that will occasionally puff white smoke when first started, but that's only when temperature's are below about 50 degrees. It's hard to say about the gray and black smoke caused by acceleration...black smoke would be diesel that's undergone combustion, but hasn't been completely combusted, while the white/gray smoke could be a sign of either too much fuel or worse...a sign of coolant being introduced into the exhaust.
When you say it knocks all the time when running...I'm not trying to be a smart-a$$ by saying that that's what diesel's do, but by knocking, could you elaborate a little more on what kind of knock you are hearing? Please try and describe it so that we can get a better idea of what's going on. I'm not trying to tell you there is nothing wrong with your truck, but I'd hate for you to have to spend money on something that doesn't need fixing. Let us know!
Later,
