Check out www.tirerack.com. What you need to do is determine the diameter of your tire. then find a size that you want. i have found on that site that you can put in your tire size (i.e. 255 55r 18) or whatever and then look at the tire details and see its diameter. On my disco 1 i junked the stocks and stuffed 245 75r 16's under there. The front rubbed a bit but after a neat trim....buttah!
"Out of every one hundred men, ten should not even be there, eighty are just targets, nine are the real fighters, and we are lucky to have them for they make the battle. Ah, but the one, one is a warrior, and he will bring the others back"