[dubie]

The only reason to adjust the caster by anything more than 1 degree would be if the truck was lower 3-6" from stock ride height. Being that yours is stock height and all you're doing is adding in a power steering unit, shouldn't make that much of a difference. I lowered mine 6" and the difference between driving with a shim and without, was extremely noticeable.
Did you drive the truck before tearing it down or was this a rebuild project from the start. If you did drive it before, did the steering wheel always come back to center after you turned a corner? Did the truck track straight and true(as straight and true as a kingpin truck can go) no matter what the speed? If so, then I would put the 1 degree shim back in, just to return it to the way it was. Then take the truck for a test drive. Once you drive it, you'll get a fell for everything. Your next stop after that should be for an alignment