This project started life as the orange toy from Target shown below. The body is pretty close to 1/24 scale. I took a Dremel to it and cut off the fenders, grill, and sides of hood. I opened up the windows more to give it the authentic modified look. All of the decals were made on the computer and printed on decal paper. The basic chassis design allows the side pans to float, which produces better handling.
The motor/axle bracket was made from sheet brass, bent in a U shape, and soldiered to the base pan. I used pieces of popsicle sticks bonded to the bracket with JB Weld for the axle bearings. They work really well and show no signs of wear. The axles are piano wire, tires are silicone-coated sponge tires, and the motor is a Falcon. The plastic motor came out of a 1/24 scale model and the radiator was molded with modeling clay and fiberglass resin. The driver and air cleaner were also molded from fiberglass resin. I made the roll cage from wire used for suspended ceilings.
As you have seen on my other cars, I use modeling clay and fishing weights for ballast. They are easy to remove and replace to tweak the handling. You have got to try the popsicle stick bearings; you will be amazed!
I make use of everything I can with scratch-builts. The front tires/wheels are the ones that came on the toy. I took two tires, filed the backs down, glued them together back-to-back, and drilled the axle hole. I used a Sharpie to blacken between the spokes. They may not suit everybody, but they worked for me. Two or three of these side by side on the track are a blast to drive!