What's the largest size tire that will fit on 04-05 FX4 with 2inch level kit??
285/70/17 or 315/70/17

 

315 will rubbing onto your frame or wheel lips...some report trim some plastic off will solve this problem..its depend on your backspacing, off set blah blah!
You will find tons of infos if you do search. first try F150 2004 2005 forum.

I believe you can get away with no problem is under 305.

Nitto tera grappler 295/70/17 is approx 33.19x12ish thats good size!

Again do the search..

YOMAN!

 

Several members have fit 315/70-17 BFG's by using their stock 17x7.5 inch wheels and a 2.5 inch leveling kit.