It'll take you longer to read the article than to actually do the swap! And worse, most shops won't be willing or knowledgeable enough to do it anyway.

Also note that the chart provided in the article calculates tire revolutions per mile based on an assumption about tire sizes that is probably not correct. A 33x12.50R15 is probably NOT 33" in diameter.

For a reference, I looked up a 33x12.50 Bridgestone Dueler A/T on their website. They spec at 32.6" diameter, and 639 revs per mile (source: www.bridgestone-usa.com). I expect most brands will give you similar results, but go to your tire mfg's website and look for a spec sheet to be sure.

Using this info to calculate, I come up with a 23-tooth speedo gear (Mitsu part number MD705463) needed for 33x12.50 tires, as opposed to the 22-tooth gear recommended in the article.