Nova Door Hinges

[71Nova]

I was planning on installing some new door hinges on my 71 Nova because my driver door droops about 2 inches when you open it. I was looking at the hinges today and realised that they look like they are welded on. I can't see any bolt heads. Both sides look the same. Is this normal? It seems like it would make it almost imposible to adjust the door gap. Was it done this way on all 71 novas or do you guys think this was done by a previous owner? I have not found any evidence in my 7 years of owning this car that it was ever in an accident.