Please do not even try to use gears with that much ratio difference. The factory ratios were only .01 different front to back with the front pulling faster than the back. I know you live in AZ and don't have snow or ice, But I have driven a rig with the gearing difference you want but it was uncontrollable. Too big a difference will cause bind-up and added stress on the driveline, over heated t-case and gear lubes. I would not go as far as 10% difference. Different size tires cause the same issues.
Joe
