One thing is certain: none of the websites in the classic NFS resources thread has any content the more active places have.
Re-conversion of the Re-volt cars to HS is an alternative. The meshes are intact. The problem is that, when I import stuff into ZModeler, the normals of the tires seem to be screwed up. It MIGHT not be too difficult to solve, but it's still annoying. And then, because Re-volt uses bitmaps as textures, you have to redo the alpha channel from scratch, not to mention carefully detach the interior from the body.
Even then, the Re-volt pack only has 20 or so cars, we need many more to complete the collection. With many of the cars being unique and unlikely to ever be replicated in another racing game ever again, I think it's worth chasing after those lost cars.