I asked this question a few years ago and there wasn't. Is it not physically possible to make a 3.20 or so ring and pinion? Or is it that the manufacturers don't think there would be any demand for something taller. Manufacturers make gears up into the 5.0 to 1 range so I'd think there would be some demand for something at the taller end of the spectrum as well. Some people buy the Gear Vendors OD unit to get taller gears so I know there would be some demand. (I checked the Gear Vendors site and it doesn't look like they make a unit for my truck that is newer than 2002)

 

Why would you want to?

Overdrive gears divide torque and underdrive gears multiply torque.

The shorter gear would only gain you about 5mph at 2000 rpm's. But it would really make the truck struggle at low speeds and rpm's. You could accomplish the exact same goal by adding 34" tires; which costs about 1/2 as much money.

If you're wanting a taller FDR in 6th gear, you'd probably be better off swapping transmissions.

 

This question comes up all the time for 4x4 trucks.

The early G56 has a really short 6th OD gear which makes for a high revving, uncomfortable Cummins at freeway speeds, especially if the engine is stock.

For a 4wd since you have to swap the gears in the front and rear axles, taller tires are cheaper and are a benefit on a 4wd truck.
Even swapping in a later G56 trans is much cheaper on a 4wd.

However on a 2wd, since there is only 1 set of gears to swap, one would have to do some careful research to determine what is the best way to go.

IMO, you would not want anything lower numerically than 3.42.