215/75/15 is the closest radial equivalent to the standard 6.70-15 bias tire, 225/75/15 would be pretty close to the 7.00-15s you're running now, but would be pushing the limits of the stock width wheels and are getting difficult to get in an LT rating (really, anything under a 235/75/15 is hard to get in LT). If you're not concerned with an OEM appearance, wider wheels from a '73-'87 GM 4x4 in 15x7 or 15x8 will fit just fine, and will open up for larger tire sizes. I'm running 15x8s on mine, with a 30x9.50x15 C load tire. No rubbing at all.
