Racerguy is right about the springs tending to sag. I should have mentioned that. Good catch! When the springs sag it causes allot of negative camber and also makes caster go positive only not as drastic as camber change. O.k. the 2* offset bushing is a new one to me but I haven't been in the business now for a few years so I'm sure technology is moving forward. I gotta give ya credit, your a fast learner. You got it right to install those bushings will give you the camber you need but will not change caster. Still check your springs tho' before doing anything.
Colour your problem goes a little deeper... The alignment seems right on and shouldn't be causing any pull. The first thing I would try is to swap the front tires from side to side or if you're due for a tire rotation try that. Tires are major culprit of pull problems. That is something else I didn't mention, was that Vans don't seem to do well on cheap car tires. Cheap truck tires work a little better but I would recomend sticking with a brand name. I'm not gonna give an opinion on which because I just don't really know? All I know is that I have seen alot of people buy cheap tires and then come back complaining of the way their van handled. Enough said... Now if the tire rotation doesn't fix the problem, next I would be looking at the brake calipers and make sure there aren't dragging or sticking. Look at the brake pads and make sure they are wearing evenly. If everything is shipshape with the brakes, then I'm fearing that your steering gear is going south on you. You can try flushing the powersteering fluid out and putting some fresh stuf in. There is no real easy way of doing this, except to unhook the lines and letting it drain out. Hopefully you'll get it with the tires and it won't come to that. Good luck and I'm glad that I could help!