Need to cut back on the Backspacing a bit, push the tire out some. Wheel spacers are an option, but I would not recommend them as most people will slap on what ever they can find with out checking or changing the lug studs to make certain they have good grip on the lug nuts.
On solid axle front ends, you can adjust the steering locks to you reach lock before you start to rub. I am still learning the GMC front end on these trucks so I do not know if this is an option, but I had to do it on my Jeep due to rubbing the battery when turning with the passenger tire stuffed in the fender well. The downside is you are taking away from your max turning radius.
I hope someone else could chime in on this, as the latter option would be my recommendation.
The best course of action would be to get a different rim, one that set's the tire out further than they currently are. I'm not into rim's, I just deal with them as I need them, so I can't tell you what your current offset is, nor what would work better. A good shop should be able to help you figure out a better combination. Or they might be able to set up a good set of wheel spacers done properly.
I must stress that wheel spacers, if that is the rout you take, should not be taken lightly, they can double the stress placed on the steering components, wheel bearings, and other components, and will look goofy if you only do the front. I also do not recommend even trying them if you will ever use your truck as a truck.
