I have a 06 screw with the 5.4 and 3.73 grearing.
I like the look of the stock wheels if I went with a 2" leveling kit and an add a leaf what size of tire would fit? I don't know the stock back spacing on the factory 20's. I also use the truck to tow my boat and my car trailer so that is a concern as well. What do you guy's think?

 

I would go with a 33" tire if you tow.

 

I agree. But you could fit a 35x12.50-20 if you have a 4x4.

 

I do have a 4x4, but do you think I should still stick with the 33's if I am towing?

 

My biggest question would be what do the 20" wheels do to your towing capabilities? I remember reading the sales brochure when I bought my truck that going from a 17" wheel to a 18" wheel dropped your towing by 500 lbs.

 

My car trailer is rated at 7000lb max, so I believe that would still be well within the specs. even with the 20's. I don't know why it would make the 500 or so lb difference anyhow. The factory 20" wheels are built like tanks and I can't see how they would be less able to take the load than the 18's. I think that the factory 17" wheels are steel rims so maybe that is the difference?

 

I guess with the bigger wheel, there is more leverage on the wheel studs. Only thing I can think of. Sounds like you will stay well below the max so I say go for it.