What's a "prerunner" ?
The term "prerunner" originally meant a vehicle that was not a race vehicle, but was used to go around a racecourse prior to a race so that someone could familiarize themselves with the course, or in other words, a prerunner is used to pre-run a course.
Today, the term "prerunner" is used to typically describe a two-wheel drive truck that has been modified to handle the rough terrain of the desert at a high rate of speed. Some are pretty, some are functional, some are both. But don't let looks fool you...sometimes the ugliest of prerunners can perform like a dream! The prerunners phenomena is sweeping the west and it'd be nearly impossible to drive the freeways of Southern California without seeing one.
The "prerunner look" is obtained usually by mounting flared fiberglass fenders which allows for better tire clearance, performance or race shocks, a tubular bumper and skid plate, and bigger and more aggressive tires. That will get you a decent offroad truck, but for those who are more serious, next would come a suspension kit or custom suspension components, such as bent I-beams for older Fords or custom upper and/or lower A-arms. At this point it would be wise to also include a roll cage.
Some people don't want to stop there. More and more often you can find a truck that has been "3 or 4 linked". What this means is that the frame has (usually) been cut away and the rear end is attached via swing-arms, usually after removing the whole bed and adding fiberglass bedsides. Many people will often switch out there stock rear axle with one that is beefier. Ford 9 inch rear ends and Dana 60's are the preferred choice of most prerunners.
There are many more things you can do to a prerunner truck to make it custom...race seats, after-market gauges, custom graphics, and on and on. It is said that once a person starts building their truck the "curse of the prerunner" kicks in and that is that IT IS NEVER FINISHED!