This has been an interesting project. The creator of the model apparently did so without the expectation of 3D printing, or completely ignored appropriate conventions for modeling aimed at printing.

I've run the model through a number of iterations without acceptable results. In many cases, the appearance is good, but when analysis is performed, the model is a complete disaster. There are reversed normals and uncountable non-manifold items comprising the model.

I was able to easily remove the wheels and associated parts, as well as the seats, steering wheel and other interior components. It doesn't solve the improperly joined outer surface, nor the huge (relatively speaking) gaps around the underside of the body. Equally disturbing is the inconsistently floating glazing and trim pieces.

If I had greater skill (currently nearly zero) with Blender, I might be able to track down the non-manifold portions and tug and bend and join edges to get rid of some of the problems.

It is such an intensely complex model that such a workflow is impractical, in my opinion.

The creator of the model is to be commended for creating such a detailed work of art, suitable for many things other than 3D printing.