The Trailblazer is a straight 6, not a v6. It provides plenty of HP and torque for the job. We tow a 20' trailer with our Envoy (same thing as the TB), and have no problems. We have the 3.73 rear, and towing capacity is somewhere around 5500 lbs. I too changed the rear shocks to the Bilstein HD shocks. I also changed ALL fluids and installed an auxiliary transmission cooler. We've taken many trips with our camper and have never had a problem with our Envoy or its ability to pull the trailer. Also, tow in 3rd gear, and keep the speeds reasonable (60-65). The ST tires on most trailers are only rated for 65 anyway. When we tow, MPGs go to about 11-13, but when we unhook, we get 19-21.
Good luck!