Do you have a hitch? If so, one of those aluminum hitch tray would work great! Light weight, hold a few hundred pounds and easy to take off and store on the roof. Plus, easy to access for fuel and water.
I don't carry half shafts, that is not a trail repair, plus, I have never heard of one failing all at once?
I would recommend one of the cheap Ebay CV joints. They are fine if you don't have a front locker. <80 bucks, just in boots, boot clamps and grease they are worth that much![]()