You missed the sub section of the section you posted this thread in: "Body lift tech": Body Lift Tech - Ford Ranger Forum
TONS of info can be found in that section. If the lifted guys here, I feel comfortable in saying 75% of them are bodylifted 98+ 4x4's. AKA....your truck! You've got 30.5" tires on it now if still stock size....so 31's with 3" lift is just goofy as hell. Most go with 33x12.50's on 15x8's....and it clears it just fine.
So.....go through that section I linked above and start learnin!
Welcome to the site.