how wide are your stock wheels?
6" ? 7" ? Thats a lot of tire for a 6" wheel, it's not gonna look right and won't handle well either. 7" should work.
I've a 2005 2wd reg cab XL 2.3 5sp 245/70-16 tires, 'bout 29.5" on 16 x 8" wheels.
the most important question to ask is: will this be a daily driver, mostly on the road????
assuming you have the 3.73 gear,
going to 31s will:
reduce your brakes by about 25% (4.10s same thing)
cause you to ride the clutch a lot more
really kill any acceleration
you won't hold speed on hills without downshifting
you will definitely notice strong head winds more
you won't get better gas mileage
on a bumpy road that much weight will cause the wheels to get lots of air time, thats not good
those same bumps will cause the rear to side step a lot
you ain't gonna go fast around corners or curves no more
you will be able to get by with only 16-18 PSI in those big tires
thats bad for mileage
and worse for handling
if you try to run 32 PSI, see comments about "air time" above
now, if you spend most of your time off road, well thats a different story all together as you won't do some of that stuff.
I'll admit I like the looks of bigger tires, just be aware that for every action, there are sometimes bad reactions. you'll have to balance out what you want-vs-what you get.
Perry