If your truck came w/ 31" tires and you jumped up to 33's, that's about a 6.5% increase in diameter.

Your truck probably came w/ 3.90:1 gears. The jump from 3.90 to 4.56 is about 17%. Way over-geared.

3.90>4.10 is 5.1% which would be a lot closer (doubt you'll notice the 1.5% difference from stock)
3.90>4.30 is 7.7% which would be pretty close too.

4.10's and 4.30's should be pretty easy to find in a junk yard on Tacoma's and T100 rears, and Tacoma and 4runner fronts... if you wanted to go the used route to try to save a little money.

And FWIW, I find it hard to believe a V8 Tundra is "underpowered" w/ 33's. Need power? Push pedal. <img border="0" title="" alt="[Big Grin]" src="images/icons/grin.gif" />