Cars are supposed to be upragedable, but I don't think they've talked about car upgrades in detail yet (if they did someone feel free to correct me).
As for weapon upgrades there is some detail in this ign article: http://pc.ign.com/articles/115/1154585p1.html
some choice quotes:
"Components can be collected from around the game world and combined together to create new gadgets, assuming you've found or purchased the corresponding schematic. Each weapon will have up to four ammunition types and a few upgrades as well, like clip extenders and aim stabilizers.""When wielding the crossbow, another silent weapon, you can use regular bolts to put down enemies or switch over to electric shots. As in BioShock, firing the electricity into a pool of water populated by mutants jolts them into submission.""The wingstick, I think, is the signature weapon in Rage," said Willits. Should you ever run out of these airborne blades, more can be purchased from vendors or crafted, assuming you've managed to scrounge together the appropriate components. You don't find complete wingsticks."Basically some weapons can only be bought or crafted, there are different ammo types for each weapon, plus the usual upgrades (bigger clip, more damage etc) and there are also gadgets like turrets, RC car bombs, and lock grinders that you can either buy or build from components.
I don't know how much point is there to customize your appearance, because the game is played from a first person perspective most of the time, I guess it only matters in coop where you see each others character. Anyway the different types of armor you wear should show afaik. I don't think pockets will be in, there won't be an extensive inventory system at all, you can carry all the weapons you have with you all the time, like in any old id software game.
As for the survival elements, I don't think they are in and I've never heard id talk about putting them in. Honestly, it's not that kind of hardcoe survivalist game, it's a sandbox shooter set in a Mad Max style world.