I have a 07 Taco and I pull a 19 foot trailer. It has a load leveling hitch and has 2960 lb. Dry weight. The truck handles the trailer fantastic, but it is wind resistance that will slow me down. BTW the Taco has a 6 speed manual, 4.0L, and a 3" lift, running 33's. I am also running the hills and mountains of the Sierra Nevada's of Calif.
Now I have never max'd out the weight, but I am also thinking from an RV perspective.
Dealers (RV's) will not sell you a rig that is more than 1000 lbs, less than your truck is rated for. So 6500# rating will get you a 5500# trailer (if we are speaking of RV's).
I hope that you don't have an automatic trans, as you will be working it to death at the max rate of 6500#