[ImperialCrown]

Welcome to Allpar. This can be a common optical illusion. Driving behind these cars, it looks like it's 'dog-tracking' down the road. This is due to the different widths in the the front-to-rear track measurements.
The rear wheels are closer together than the front wheels and sitting in the drivers seat of the following car gives this visual impression.
As long as the unibody frame isn't damaged, it is just how it looks down the side of the car. Do some diagonal (X-points) frame measurements with a tape measurer if you have doubts.

 

[Bob Lincoln]

My brother had a 76 Feather Duster, and we knew when he bought it that it had been hit by the RR wheel; there was a lot of bondo there. One day I was driving behind him and noticed that I could see all 4 tires - it was not tracking right, the rear axle was offset to the left by probably at least an inch or more.

If the car has had body damage, do as IC suggested, a diagonal measurement will reveal if the body is bent.

 

[TWX]

I actually have had "doglegging", I needed new bushings for the front spring eyes on my '78 Chrysler Cordoba. Old ones were messed up, and that car had really big, oval-shaped spring eyes to make the ride better.

 

[68RT]

Double check the bolts that hold the center of the spring together. The head of the bolt is also what holds the rear end centered. If either spring's bolt gets loose or the head shears, the axle can shift and it will be "dog-legged". The bolts must be straight up and down in their orientation. Not that hard to fix.

 

[KOG]

Not only is the rear axle narrower thatn the front on A bodies, it's offset. But since the engine and transmission are offset to the right this all seems to work out.

 

[ImperialCrown]

A quick measurement with your tape measurer and a helper, would be to compare the right side wheelbase with the left side wheel base at the front hub-to-rear hub centers.