northern 85,
The tires are 275/60-15's in the rear. They fit in the up in the bed just fine as long as the truck is not overloaded to much. The panyard bar in the rear pushes the rear axle to the driver side if i remember correctly causing the drivers wheel to rub the bed. The fix would be to either shorten the panyard bar or buy an aftermarket version that is adjustable. I do have factory Auxillary Springs (G60BC AUXILIARY SPRING EQ) on the truck so it doesn't squat as much as most half tons. I wouldn't go any wider on the wheels without increasing the back spacing of the wheel itself. The rear wheels are factory 4x4 blazer wheels 15x10 i believe. The tires are 275mm wide which converts to 11.25 inches tread width.
