Though seatbelt and child seat laws came into be in 1970, official baby car seats were just coming out in the late 70s. Or if they were out, very few people had them.
I got my license in 1977 and my little nephew was still in this little sitter thing that had two curved extensions that just latched over the back of the front seat. It was the most dangerous thing ever. You sit there - high up so you can see out - but nothing to hold you in.
I remember having to slam my brakes and my right arm instinctively extended to the side to keep him from flying out.
Does anyone remember those baby seats? Reminds me of the kind you attach to a table so that little ones can sit there and eat.
I saw one a few years later and a woman had her poodle in one.
I'll try to find a picture of one.
ETA: It looked something like this. They were very popular. I think this one is for a table, but the car ones would just hook over the front seat - no seat belt whatsoever went through it (from car) though some had a little belt on the seat itself. And you couldn't use this in the backseat. They came in plastic and with canvas seats, so the baby's bottom just rested on it.
In 1979 when I did rotations in clinical nursing - maternity - we "recommended" to the parents to buy a baby car seat. But it wasn't the law yet. It wasn't until a couple of years later that we wouldn't let them leave the hospital unless they had one.
I also remember little ones in a carrier, just sitting on the floor of the car - usually the front seat so that the driver could watch them. If there was a second person, the person carried the child.