Are our Slants "Unsafe"?

That is so stupid. It should be a law that you have to retrofit your vehicle with seatbelts.

That's how it is in most of Australia, and they have a thriving old-car hobby, so that puts paid to the bogus "nanny state" thing. Certainly cars that are ever driven in traffic on public roads, no matter how infrequently, ought to be fitted with good belts—law or no law.