Basically just study the photos, and think about racing in general. I dont really have any first hand info on any of this. Im just working from the photos myself. First and foremost, put the tank in a safe place behind the cab. Move anything thats gonna cause wind resistance. Some of these guys were chopping bumpers, chopping fenders, shortening the wheelbase, and adding bars to protect various parts of the truck. Some had custom exhaust. I made my rollbar from solid evergreen round stock heated and bent into shape a little at a time. The roll bar on the Pete was made from square tubing and "I" beam. Keep in mind, there were no high performance truck parts, they raced on highway tires. So any mods would have been homemade, meaning that you can make it too, only smaller. Just pic one out of a photo and have fun. I havent reproduced any one in particular, Im kinda just compiling ideas and making fictional trucks.