Since you have looked for all the bad signs (oil condition, coolant contamination, pressure in radiator, oil pressure good, etc) sounds to me that the smoke is simply from lack of running. One trick to know which cylinders are firing and which ones are not is to start it and check the exhaust ports for heat. Obviously they should all feel about the same. A cold one or two might not mean much until the truck is warm, then becomes important. A cold cylinder indicates no fuel (or drip, no spray), which points to injector problem.
I have had to start up engines that have set for years, too, and white smoke is common. Because a Diesel is slow to warm up unless it's working, I'd suggest it just needs to be driven. It probably has not gotten up to good hot internal temp yet. Maybe not go out and hit the freeway yet, but drive it for an hour and see how it goes.
Best of luck,
Bob