One thing that is often overlooked when replacing the pads and/or caliper is the caliper pins. If they are not cleaned and well lubricated (I use brake caliper grease) the pins hang and cause the caliper on one side to not "float" and close as well as the one on the opposite wheel. This will cause the truck to pull toward the "good" side. Sometimes the pins get stuck so bad that they cannot be removed and the whole caliper bracket has to be replaced. Always be sure to clean and lubricate those caliper pins.