I cut the hell outta my fenders and came close to fitting 33-12.5R15's with a 3.75 backspace on the wheels. But that was only driving on the street.
I currently have the 3" Skyjacker kit, and i WOULD NOT recommend their products.
I've been running it for about 4 years now.
When i first put the kit on and my 31's, within the first month I wheeled one long weekend and the rear springs sagged so much i had nice shiny spots on the inside of my rear fender wells where the tires were contacting. I went to a local (to me) suspension shop and had them add an extra leaf and re-arc them all. That problem was solved.
Within a year, 2 out of the 4 shocks were smoked, i replaced all 4.
Then about 6 months after that, the bracket for the trac bar cracked and broke. Had to get it reinforced and welded up.
That's a real-life experience from a guy that wheeled about once a month on average during that time frame. And i wheeled mostly mud and didn't jump it off rock ledges or anything crazy.
I'm going to a 4.5" RE lift because i have heard and read many good things about the quality of their components and it should allow me to run my 33-12's. But like i said, i have really cut out my front fenders, but haven't touched my rears yet. I would go to the 5.5, but i would like to keep the center of gravity as low as possible.
A good tip from a friend of mine is to bend the sheet metal back instead of just cutting it and leaving a nice sharp edge for the tire to get cut on. I've done almost all the cutting, but have a few more spots to shave off. Then i will make some "relief" cuts in the corner areas of the sheet metal and bend it back into the wheel wells. When i finish i should have a rounded edge and limit the possibility of cutting my tires if they still rub.