A programmer with a program burned specific to your application would help maybe 15-20hp/tq. The programmer should also increase the shift points and shift firmness which will help more than the extra power. Some extra gear might help as well.
for about the same price as a programmer or custom chip, you can have a local shop (that specializes in differntials) change your gear ratio to a higher numerically gearing which will, in my opinion, help your trucks towing capability far more than any chip or programmer.
depending on what you have as a gear ratio, anywhere from a 3.08 to a 3.73, going up one step from say a 3.08 to a 3.23 or 3.55 would be a huge improvement and since your truck is 2wd there is only one gearset to replace. You can buy gear sets from summit for about $150-200.
here are some suggestions for gear ratio changes (depending on what the current gear ratio is in your truck) A more significant change will result in better towing characteristics for your truck.
I will assume that your trucks factory gearing is one of the ratios listed on the left. a higher jump in gear ratio change will give a more significant towing advantage but going to high makes you engine rev excessively at highway speeds (even in overdrive) and you will burn significantly more gas. I am also assuming that your truck has the 4 speed auto overdive and a 29" - 30" tall tire.
figure out what your trucks gear ratio is and let me know.