I have a 2006 XLT with 3.55 gears and I am going to be getting 35" tires. I am currently running General Grabber 33" tires. I will be getting 35" BFG all terrains. Most sources i've found say I should re-gear to atleast 4.56. However, the tires I am currently running are about 72lbs each, the larger BFGs are about 65lbs each and I think they're a bit narrower. Do I need to re-gear? If I do, I'll probably go with 4.10 gears because I drive this truck on the interstate everyday. Thoughts?

 

I think you are on the right track. 4.10s will be better if you do lots of highway driving. Here is my thread from when I did mine.
https://www.f150forum.com/f4/new-4-5...-tires-161334/