I tow a 12,500lbs 5th wheel and currently have a 3.73 rear end. What I'm looking for a little more ease starting out and to raise the RPMs vs mph when towing. I feel that my truck likes to run at about 2,000RPMs and with a 3.73 rearend that is 70 MPH, a little too fast at a GCW of 20,000 for my...