Everyone (bloggers and the guys a 4 wheelparts) said i would have to get a 6 inch lift to fit 35" tires on my '05 FX4 without any trimming. I was able to fit them using Rough Country's 2.5" leveling kit with rear blocks and shocks. The tires are 35"x12.5"x18" Nitto Trail Grapplers and the wheels are 18"x8.5" ATX Crawls with a +15 offset and 5.34" backspacing. Even rough country said that some trimming would probably be required. It's been a month and so far they have not rubbed and it looks great. I can't believe more people haven't figured this out.
Sounds like you hit on a good combination in terms of backspacing, lift, tire size, etc. Sometimes you just get lucky. Thing is, they have to make recommendations for off-the-shelf installs, and that's why they may recommend trimming in some cases.
You're right about the luck. I bet against the odds and won. I just hope my post will help others realize that they don't need a $2000 suspension lift in order to use 35" tires. Thanks