A while back, I bought a 1974 chevy k-5 blazer body for my rock crawler. It was cheap, like $20 on eBay, but it isn't exactly what you would call scale worthy. Its just a shell, so I added things to make my body more like the pro guys have such as fender wells and lights.
Step 1: Inner Fender Wells
1) Use a wire to make the shape of the fender and use this as a guide for making the actual fenders. Write down the length of the wire
2) Decide how deep you want the fenders to go into the body and cut a strip of coroplast that width and the length that the wire was.
3) Cut through one layer of the coroplast to bend it in the spots where the wire is bent. This should make the coroplast have the same curve that your fender does.
4) Glue two up-right pieces in the body so they are the distance to the edge of the body is the same distance that the fender well is wide.
5) Glue in the fender wells. You can run a bead of glue along the inside seem then lick your finger * and push it in the crack to get the glue in deep. This also makes it look better.
6) Make covers for any other areas you want by cutting through one layer of the coroplast allowing it to bend to the shape you want.
7) Make a bunch of supports and glue them in.
* Just warning you, if your finger is not licked, you WILL get BURNED.
Step 2: Rubberized Undercoating
1) Outline the area you want sprayed with tape, like giving it a border.
2)use paper to cover the rest of the area you are not going to paint so you dont get over spray on it.
3) Scuff the surface lightly with a scotch bright or 2000 grit sand paper.
4) Spray from about 3 feet away but dont try to make the first coat cover.
5) Wait till the first coat dries then spray again until the desired look is achieved, most likely 3 coats.
6) If you dont leave it in the sun immediately after you spray it, it will never dry. Ever. It usually takes 4 hours for my stuff to completely dry.
Step 3: Lights!
I get my lights on eBay from a guy who is called RCLightHouse. They are pre assembled and come with a 9v battery clip. These lights make the truck look so much better.
1) Get lights that you think will make your truck look nice
2) Find a drill bit that is a tiny bit smaller than the metal light socket that they come with.
3) Drill holes and push the light through, should fit tightly. Use needle nose pliers to tighten the little nut.
4) Find a place to mount the battery.
5) Add more if you need em!
A switch is also a nice thing to have installed before you add the inner fender wells and the wires become extremely hard to access..
Step 4: Haul Stuff Around
1) Decide how big you want your trailer and if you want a tailgate.
2) Use simple math skills to determine the perimeter of your main trailer and the tailgate.
3) Buy that much or more, 1/4 inch aluminum angle from a hardware store. Make sure to get a few extra feet, i got 8 feet for $4.95 at Lowes. I ended up needing 10 feet for the hitch and the fenders.
4) My trailer was 1 foot by 2 feet. I wanted the ends of the frame to meet in the middle, so I made a few marks.If you laid the piece on the floor, there would be one side sticking up and another side laying flat. Mark on the side that is laying flat. I made one at 6 inches then one at 30 then one at 42 and 66 and the last one at 72.
5) I used metal sheers to cut a little triangle out of the flat side so that the side that was vertical was still intact, but I could bend it so that I would have a nice round corner. Because i put the place where the two ends meet in the middle instead of on a corner, all the corners were the same shape.
6) Use the smallest metal lath you can get your hands on and cut a piece that would fit tightly in to the aluminum frame you just made.
7) Drill a hole every 4 inches down the long side and every 3 on the short side and rivet the lath to the aluminum.
8) Fabricate your supports for the axle and use threaded rod with locking nuts to hold it on.