4.10 Or 3.73

[DHoy]

About to order a 2005 600 and need some help. I'm geting a 3500 with a auto 2wd 8ft bed. My 5th wheel is 12,000lbs dry. I guess about 14,000 loaded. Should I get 3. 73 or 4. 10's. If I go with 4. 10 what will be my rpm's at 70mph, and if I have to run out of overdrive what will be my rpm at 65. Most of my towing will be in TX but there is always lots of wind. Thanks Denny Hoy