Are backseat safety belts standard for 1967 volkswagen karmann ghia?

No, and not optional. In fact the "no back seat belt" question was answered the last years of production by eliminating the back seat.

The back seat was intended for lower insurance rates by claiming 2+2 under body style.

It is my understanding that Karmann Ghias never had backseat safety belts, as the backseat area was intended for cargo (i.e. groceries, luggage, etc.) but not for passengers.