Crooked K-Member

I bought a brand new cuda in 1970, that was wrecked before I took delivery. I'm still the original owner, but it had the left front fender replaced. Some people might not know the difference, but I can see all the evidence. I'm not saying that is your case, but what I am saying is, it happens.
Actually, a 1/2" difference doesn't sound that extreme. You said, yourself, that it wasn't noticeable with stock wheels/tires. Well, that's the way it came off the line, and if it looked OK then, and worked OK then, that was good enough for them back then.