Your axles can't be regeared to a ratio lower than 4.88 so 5.13 is not even doable. I would stick with 33" tires and 4.88 gearing which is as big of a tire as your 2.5L engine can handle without losing too much power.
Yes you need two sets of ring & pinion gears, one per axle. But don't buy them on your own with expectation to supply them to the installing shop. If you do and something goes wrong, the installer will blame the parts you provided him and not cover them in his warranty. And then the parts provider will blame the installer and not want to cover them either.
Have the shop provide EVERYTHING and then their warranty will cover anything that goes bad which does happen. One of my R&P jobs went bad 3 weeks after completion and the shop covered the whole thing without drama because they provided all the parts and labor.