They will change after they are loaded. I would not change anything except getting the toe in close until I had the truck done to the point where all the weight was on it and it had been driven around the block.
If you bought a dropped axle from Nostalgia Sid it should be set on the money for what an I beam axle should be set at. If it is the Speedway junk all bets are off or if it is an old used one you don't know what it has been through.
All of the older skinny tires rigs before about 1980 ran positive camber. Cadillac Deville was the only rig that called for negative and that was 1/4 neg on the passenger side tire. Most of those early Mustangs called for 1 degree positive. Neg camber didn't come into play until later when cars like my BMW 528I showed up with it so they could cut the corners better. That was a whole redesigned setup from the older rigs though. Simply meaning because your late model performance car that you drive daily has negative camber and the past three cars before that did there is nothing wrong with an I beam truck having positive camber as long as it isn't excessive.
Adjusting camber on an I beam or "straight" axle takes setting it up on the alignment rack and actually chaining it or using designed hooks to tie it to the beam on the rack and then applying pressure with a bottle jack in the right place to move the end of the axle where you need it to be. It's a long way from rocket science but one has to know what the heck he is doing so as not to screw it up.
Again, don't worry about it until the truck is all together and derivable. Outside of sending it to Sid to be checked and corrected there really isn't much one can do with it beforehand.
Some vendors sell an inexpensive caster/camber gauge on Ebay that might help in the preliminary setup and checkup on any build and for 15 bucks they aren't that bad. I haven't compared the one I bought against my SnaoOn Caster/camber gauge yet but it looks like a viable thing to get close with .
https://www.ebay.com/sch/i.html?_fro...gauge&_sacat=0