If you are talking automatic 4. 10s are the only gears to have, these engines pull best above 2000rpm, with the 4. 10s you will be spinning 2150rpm at 70mph with stock tires. 70mph is a little fast for me when towing so I often drop to 3rd on hills as it get's out of the power once below 2000rpm.
If you are also planning on putting larger tires on you definetly want 4. 10s. Running empty with 4. 10s the rpms can get up there, it won't hurt it anything, but 2500rpm can get loud and buzzy on a long trip, that is the only time I would want to have 3. 73s.