That being said, the .P3D and .PTX files use RIFF as a container, but I figured there's more to it than just that. Maybe some of you 3D experts could figure out how to break this down so that we could port these cars to some other game easily.
Here are sample files I extracted using the BMS scripts mentioned above:
https://www73.zippyshare.com/v/vcUnAAjj/file.html
https://www73.zippyshare.com/v/AauPpLjC/file.html
EDIT: I opened the P3D and PTX files using Riffpad and the nodes seem neatly laid out and labelled (vertex positions, vertex normals, tangents, vertex uvs, indices...). Then again I'm not an expert with deciphering them floats and vert positions so I'll leave those to whoever can understand them:
