The original was really close but had a few issues that I corrected most importantly making it use at least a PART of the required by pinewood block per the Cub Scout rules, and making sure it stayed UNDER the pinewood derby car size requirements (7" long MAX and 2.75" wide max). I added a few other embellishments to the driver compartment including a dashboard, center console and drive-line "hump". Made the model "self supporting" so you will not need your slicer to add support material if your printer is working right. You will need to size your block to fit in the cavity and that should leave just enough wood for the wheels to attach to the wood block as is required by the rules.
This thing was made with Tinkercad. Edit it online https://tinkercad.com/things/a16IVAlGRN8
-Perimeters are set to 2
- Infill can be 10% or .1
- No support needed
Pictures are from a Printrbot Simple Maker XL using PLA.
Cut your pinewood block down to minimal 5/16" tall in the center but 1/2" at the wheel attachments, by 6" wide, and width is stock 1 3/4". Use the additional "template" file as a guide. Be sure to line up the wheel slots to the centers of the wheel wells (should only need to cut of one end of the block to get the length).
Note: If you work on the original Tinkercad files, you will likely need to use a repair file to fix the mesh. I've upload files that were run through Nettfabb Cloud at https://netfabb.azurewebsites.net/