There are a few members here that have done this.46GMC comes to mind.Maybe he will stop in and give some info.I know he does have 3-1/2" back spacing and 10" wheels.You might need to give more info as to where the tires are rubbing.( inside on frame,on top against the fenders)

http://s532.photobucket.com/user/tzkjoker/library/Truck?sort=3&page=1