gears are your biggest concern. ive got an intake and trinity, and I'm gonna take both of and go back to stock here shortly to test my mpgs. My 4:10s in the rear plays out quite well when I'm towing.

 

I suggest upgrading to a diesel truck if towing is a major concern for you.
I dont believe there are 5.7 perfromance upgrades available that will benefit you for torque/towing application without paying unreasonable amount of money and fighting with tuning/programming within the dodge ecm.
Dodge did theyre best to balance hp. torque. economy and reliability and anything you do to upgrade will compromise that balance.
the cost of a sc plus install, tuning, transmission upgrades etc would cost almost as much or more that the diesel option on a different truck. and you'd end up with unmatched torque towing power and reliability with the diesel.

good luck with whatever you decide

 

What are you hauling in that trailer? Reason I ask, I have a 25ft NRG toy hauler. We had a Kawi side x side, two 450's in the bed of the trucks, a klx110 pit bike, full fresh water, and stocked with coolers. This was with a 2002 ford f350 7.3 diesel. On the scales, that sucker topped out at 21,000 pounds. Figure the truck alone weighs 9,000. That small 25 ft trailer weighed in close to 11-12k pounds.

Like us, your trailer may weigh WAYYYY more than you thought and the truck is doing fine, its the over weight trailer thats the problem. Anyway, you biggest benefit would be the getting the highest numerical gear ratio you can in your diffs. I think 4.56s.