810 812 Heads

I have been looking at a new set of heads for my 812 engine and noticed something. It appears the designers did not make a left and a right head. Is this a fact? I recall several other items were not made for a particular thing like only 2 doors were made even for the sedans. A right front and a left front. Then they were cut down to fit the back door opening. Can anyone tell me of other parts that worked as a double like this? Thanks.