We will be traveling thorugh Zion, Bryce and Torry? Anyone have sugesstions?

Never have been, but my bro in law who modifies jeeps for rock crawling always goes to Moab,Utah.

We have a friend with a Hummer and his "Hummer Club" takes trips - from the east coast to Moab.

The Shafer Trail and the Long Canyon Trail are good trails; I've only been on the latter and it was neat.

There is a book called something like Best 4wd drives in Utah, which I think you'd find very helpful.

If you mean 4WD cars as opposed to ATVs, I'd also recommend Moab, as well as the Needles District of Canyonlands NP, about an hour south of Moab. The White Rim trail near Moab is very popular with 4WDers and mountain bikers, but it's controversial. There have been environmental protests against taking jeeps there.

Thanks, I'm sorry here we call the ATV a four wheeler. I'm not looking at a Hummer or Jeep but the smaller single passenger off road Honda type.

I don't think that ATVs are usually allowed on NP roads, but national forests are usually good bets. You might want to look at the Manti-La Sal National Forest, also around Moab.