What rear end ratio do you have? That'll make a big difference in what size is best. Wiith stock gearing (probably a 4.10) I'd go with either a 31/10.50X15 or an LT235/75R-15. They measure out pretty close in diameter,but you'll still want to stick with the same size on all four. My first choice would be the 235's. ask at the tire shop;they might know of something close to the same width but maybe a little taller,that'll help keep the rpm's down on the open road.
