Like Landshark said, you have to open the caliper up to fit the new pads in. The caliper pistons need to be pushed back into the caliper housings. Use a C-Clamp to push them back in. Then you'll have planty of room for the new pads. Now... REMEMBER TO PUMP THE BRAKES BEFORE MOVING THE TRUCK!!! The pedal will drop to the floor a few times until the pads reach to rotors again. You won't have any brakes until the pedal is hard again.
Joe