I have said this for a long time but now I documented one. The body plugs came from the factory both ways. Most often the humped part is up but they can be down and I have seen them all ways after I started paying attention to it. Here is a survivor car and has them both ways. I am not pulling the carpet to get a top view but from the bottom you can see one of each. This is a 1970...

 

Good info. I figure these were one of 'those things' that rookies or lazy on the assembly line occasionally got wrong and just thought 'Meh, close enough'.

Aw, c'mon!

 

lol, It's not my car. Just working on it for someone.