I had a buddy who ran 33x12.5 and 33x15.5 tires on his FJ55 with rearched springs. IMO, the 15.5 were too wide, but the 12.5 looked good on there. Not honestly sure on what rim setup or fender adjustments were required.
I've seen 33x9.50s on factory wheels with no lift and they clear fine. I would think you could get away with 10.50s I have 12.50s on my 55 with a 4" lift. when I stuff 1 front with it turned the ouside of the tire rubs on the lip of the fender where the front of the fender curls back.