Yes you should see some improvement with a power build-up of the 22re, but wont reap its full potemtial w/o regearing for the tires you want to run. Given the weight of Toyotas, absent dropping in a 300hp motor, regearing is the best bang for your buck.
You can also get 4.88 oem diffs, though a little more rare than the 4.56's, however, if you want to run a locker in the rear, you will want to have your rear diff regeared. I am not sure of the 4.88 diff was an option w/the 1st gen Taco's/3rd gen Runner or if it had a factory locker, if they did this would be another option for the rear. Regearing the rear diff can be done for just a little more than buying used diffs from a parts house, when you bring the diff in and only pay for bench labor. Keep an eye on craigslists and the 4x4 boards, there are often good deals on complete diffs w/gears and lockers, or uninstalled gear sets.
