Nitto Terra Grapplers or Nitto Trails?
#18
#19
That size tires will not look very good at all with the six inch lift you have. If you aren't too attached to the truck, I would look into trading it, if you are worried about mileage or get a cheap commuter car. Those tires will fit on stock rims, but stock rims won't work on your truck with the modified suspension. Specific backspacing is required for lifted trucks that stock wheels don't have.
#20
#21
#23
Maybe you are misunderstanding, you can drop to a 17x9 custom wheel, but it will need to be low offset such as -12, but you cannot use 17 inch stock (that originally came on the truck) wheels.
#26