I believe the factory antennas are going to be the least of your concerns. if the body of the truck is plastic, you will need to create a mount for a dipole, or gut the interior of the truck and line the inside with a metal foil to bond everything together.
those factory antennas will work fine under ideal conditions, but how the body is constructed, and how and where the antennas mount will determine the performance more than the antennas themselves. take an ohmmeter and measure resistance from the antenna mounting location to the ground side of battery. if you see more than 5 ohms you have more important issues to rectify before buying antennas.