For a Bogger, you want to get a truck that's 4x4. Build a roll cage out of round stock. A racing seat. The madd mudder engine would be good since it has the zommy headers already. You want to make the truck have a low center of gravity, but big tires. The best tire would be the 44 ground hawg, since it will come with the kit, but if you want realistic, then get the so real 44 boggers. This should be an easy build, but it's going to take things from multiple kits and some scratch building.
If you want a certain truck, then just check ebay or local hobby store. If you need reference pictures, then look up mud bogging racing pictures on the internet.