Skyjacker says that a 37" tire will fit with their 5" kit. It is actually a 4. 5" lift for the diesel trucks because of the extra weight. I would think that height wise, you would be o. k. with the 6" kit and a 38" tire. You might run into trouble with the width though. If you get a wheel with a normal offset, you'll end up with around 4. 5" backspacing and that makes the wheel and tire stick out quite a bit. with a tire that is 15. 5" wide, you probably will be hitting fenders at some point when you turn the wheel.
I'm going to buy the tire and wheel I want, get it home, then determine what size lift I need.