Mark Miller airs out his Chevy Silverado "Prophy" truck en route to a Trophy Truck class win. What's a Prophy truck? Mark originally purchased a Protruck to use as a prerunner during his stint as a GM factory team driver. When GM suddenly cancelled its off-road racing program, Miller was left without a race truck. Rather than build a Trophy Truck from scratch, Miller and UMI Racing made a few critical mods to the Protruck and jumped headlong into off-road racing's biggest league. The engine? A 6.0L GM crate motor with stock fuel injection. The tranny? A stock GM 4L80. Other departures from the Protruck platform include Brembo brakes and BFGoodrich tires. Admittedly, the UMI Racing Silverado gives up 200 hp and several inches of suspension travel to the scratch-built ueber-trucks, but race results speak for themselves. Having previously won the 1000 astride a motorcycle, Miller teamed with NASCAR and off-road talent Ryan Arciero in search of a four-wheeled victory. The pair followed a game plan put in place by team manager Don Tebbe, who also worked with Miller on the factory GM team. A loose power-steering fitting in the early miles left Miller guiding his truck on arm strength alone and near exhaustion when he handed off the truck to Arciero after 440 miles of Baja terrain. Special thanks go to Athletes Performance for getting Mark in top shape for the Baja 1000.