Honestly, sounds like justification to get the new car smell again....nothing wrong with that , but an even 2 tons in the back of a new long bed 1 ton is well within that truck’s wheelhouse unless srw stability scares you.
Air assist rear, I’d skip for hauling a TC for the reasons mentioned, but if you get the dually you won’t need any extra suspension.
HO/Aisin. Personal choice. It’s now a significant bump in torque that you can’t mimic with a SO engine without tuning. Trans is stouter but the 68 will do want you need. Most of the upcharge is for the trans. The cost for the additional power is negligible. Easy tuning.
Dual alternator? Heck yeah. Then you can run a dedicated charging circuit. Tap in with a big fuse and a charging relay and hooker up. If you really wanted separate alternator for camper, have the truck re flashed to single alternator and wire it Direct, with a charging relay.
Gears, 3.42 will pull a lot. Since you have the money, get 4.10s. Will pull it mo betta.
Have fun w the new rig!