1965 Dodge Dart 270 2 dr sedan

Volvo was the first car company to introduce the three point seat belt in a production car in 1959. It was invented in the USA in 1951. Volvo improved the trans tunnel mount and got that part of the invention patented but the invention itself was already patented in the US.

Seat belts in the front seats were only required by law in new cars from model year 1970 (rear seats from 1971) so they were likely added later. It became obligatory to USE seat belts in the front seats in 1975 (rear not until seats in 1986).

But Ulf may know a lot more about this than Wikipedia does. :D