Dan is absolutely correct. The Monster Moto Shield
will work with this chassis but that shield only has two channels for motor control. What that means is, with just one of those shields, you would really only have "tank controls" meaning one channel is controlling the "left" motors and the other is controlling the "right" motors.
Another DC motor driver we have from Pololu, the Motor Driver 15A IRF7862PBF
could work it is designed to drive a single DC motor so you would need one for each motor on the chassis. The Pololu Product Page
will have the most information on the specifications and instructions for that driver.
Unfortunately, since the motors on the Wild Thumper Chassis have a stall current of 5.5A, the Monster Moto Shield and Pololu driver are realistically the only DC Motor Drivers we carry that has the capability to effectively drive those motors. There are other options that could do it, but I would not recommend since that stall current is so high.
I hope this helps you find an appropriate motor driver for the Wild Thumper Chassis.