You stated that your truck does not have the tow package, does it have the off road package?
If you race almost ant type of cars you should be able to figure out how bad the towing gear ratio gets with "bigger is better" tires....and the stock rear ratio of 2.94....
If you race almost ant type of cars you should be able to figure out how bad the towing gear ratio gets with "bigger is better" tires....and the stock rear ratio of 2.94....