Seat beelts were requiired by law in the US starting with the 1967 model year. Remember Nader`s book ;Unsafe at any Speed; came out in the mid-60's.
Also, the 1967 model year was the start of unleaded gas in the US.
Impact bumpers came in 1973, just as the R107 was rolling out. Remember, no 1972 W113 or R107.
Generally, I don't study history--can't see much future in it.