I do not know much about suspentions, but assuming the balljoints, steering linkage, camber, springs and all are in good shape and not the cause, you still have to deal with the fact that the path the tire travels at is a curve or arch. If they are aligned perfectly when empty and you add a bunch of weight, they `squat' and following that arch, and will wear the insides. This happens when you brake too, and cornering, as it basiclly adds weight to the front suspention. If it is the other way around, it will wear the other way. Wear on the outside will happen on any axle setup though if you corner too fast or drive aggressivly (like everyone does). You can tell the alignment guy to put a little negative camber if that is you, or a little positive if you are a granny. Shot springs sound more like a worn inside (neg camber). If you have the outside worn, I would get an alignment. If the springs are shot than you would not even be able to adjust it. I think about . 75 to 1 degree is what you want. And do it when you have the truck at the weight you always have it at, or have it compensated. A straight axle only has to deal with cornering wears causeing the whole axle assembly to tilt. Shot saggy springs seems like it would not wear the outside, but the insides, so that is why (assuming you don't drive like stomp does) you probaly just have the camber set a little too positive.