Reading between the lines, I don't get the impression he filled out any paperwork for the ability to transport a fully functional jet engine on the back of his otherwise totally normal 4 cylinder production VW beetle.
The fact it turns on, is bolted to the vdub and so forth... mere details.
Converting a car is a completely different kettle of fish. As someone who's built a couple of personal electric vehicles I can attest, the US has plenty of regulations of what you can do on the highways and byways.