I have Hankook M/T 315/70-17's on my 06 250, which is classified as a 35" tire, and they look great. I have the 2" Newton lift on the front and two homemade machined blocks on the rear. The rear blocks are roughly 1 1/8" thick, which puts me almost level, maybe a little high in the rear, but you can't see it. Have had no trouble clearing the tires so far. As for the 37's, I am not sure, but I know you can clear the 35's. Some on here say you can clear 35's on the stock 20's with no lift. but I don't know. BTW, my truck came with the stock 20's, but I bought a set of aftermarket wheels when I put the Hankooks on.