The stock wheel size is 16x7 for any of the 16" factory wheels. The 17" ones are 7.5" wide.
Actually, the 255/70/16 IS the factory size for the 16" wheel.
You can easily go to a 265/75/16 (~31" tall) and the max would be a 285/75/16 (~33" tall) without any modification to the suspension.
Now, even going to the 265 will put your speedo/odo off by some 5%. When I put on the 265's I had to get a new VSS gear with one less tooth to get the speedo/odo (and the trucks shifting characteristics) back in order.
This is an older shot, but this is what the 265/75/16's look like....