NVEli

Hi, I have a 21 NV 2500 with the 4.0 V6, 5speed auto, 3.36 axle. The 4th and 5th gear lockout make towing less than ideal and 3rd is to low on the hi-way. Will a higher axle ratio help and what is available if so? Also would the 7 speed auto bolt up to the V6 and would that help? Thanks