you preferably want one that came withe the tow package... aka (6 pig plug, Hitch, and trans cooler)
Tow package is a must. In addition it adds a stiffer suspension. When I first got my camper I had a 2000 2wd Silverado that didn't have the tow package. Talk about scary. That thing was all over the place. My 01 Suburban had 242,000 on it when I traded. No motor or tranny problems. The 05 Denail XL I have now has 145,000. Motor runs like a champ and has nice power. The tranny (maybe the torque converter) is starting to have issues though. You might get 10 mpg when pulling, more likely 8-9 mpg. I have gotten as low as 6 with the Suburban (40 mph cross wind for 225 miles) and with the $4-$5 a gallon gas coming, it will cost a lot to pull it.