The factory alignment specs for many (most) rwd vehicles will allow for positive camber. I would get away from the factory settings and adjust yours with .5 degree negative camber. That will reduce some of the understeer that running positive camber will induce, and will generally decrease front tire edge wear. Depending on tire width (the wider the tire, the less toe-in typically) I would dial in about 1/8" toe-in. As to caster, start with about 3 degrees positive and adjust from there for how the truck feels going down the road. If the truck doesn't track well on the freeway with these settings, add more positive caster and maybe just a bit more toe-in.
I suspect the reason you have different readings from stock is due to the truck now sitting at a different ride height than when the original body was installed. Could be worn control arm bushings also, or both.