Without trimming, on a 1st gen W250 a 37x12. 50 (Goodyear MTRs is what I had) 6" using a 10 wide wheel if you use a wider wheel or tire you'll need 8+, 35x14. 50 on a 12 wide are fine with 6" 38. 5x16s on a 12" wide wheel under a 10" lift still hit (I have to put new fenders on when I get home)
Now if you trim the fenders (I don't like that look) you may get 36" tires under a 4" lift depending on wheel/tire widths.