Sonce you're going with a 3/4 ton chassis and I presume axles, I would strongly suggest using a 16 or 17 inch rim over the 15. You'll gain much more stability with the shorter sidewall. There's also a potential for brake interference, especially if you upgrade the front axle to a later open knuckle version, which I also highly reccomend if you pan on any off roading. The later open knuckle axles have a stronger spindle (7/16" bolts vs 3/8"), a tighter turning radius, and on '71-'92, disk brakes.
For tires, you might want to consider the BF Goodrich Mud Terrain KM. It's a much better tire than the Goodyear, and costs less, too.
