This model is inspired by the 1932 Ford Model B pickup truck.
The wheelbase of this model is about 1/8" shorter than the standard and may not be eligible for some races.
As with all of my builds, I'm not good enough at Fusion 360 to create a faithful replica, but I tried to capture most of the key elements.
A pinewood derby is an event created by the Boy Scouts many years ago. Each scout is given a pinewood derby kit typically consisting of a block of wood with slots for axles, 4 wheels, and 4 nails to be used as axles. The scout (and his dad, usually) will then carve the block of wood into the shape of a car, paint it and apply stickers, install the wheels on the axles, and then race it at the "derby", which involves a sloped track with a timekeeping apparatus.
An official scout derby will usually require that the parts in the kit be used for cars entered in the derby. Other organizations (including workplaces) often hold derbies, too, and some of them require the use of the parts in the box, including the block of wood.
These "pinewood derby car shells" are intended to be used with an official derby wood block, cut down to size, along with the axles and wheels included in the kit. A printable model of the shaped wood block is provided. You can either use the printed model or use it to accurately cut an official wood block down to size.
This car was smoothed with 3d printing resin and baby powder. You can find videos and guides online that describe the process, but here it is in a nutshell:
This model is designed to drop on an official wood block carved in the shape of "Shaped Block.stl". The wheel slots are slightly closer together than on the standard block, though, so you'll need to cut a new wheel axle slot. Or just use the 3D printed block if your derby allows it.