I'm getting ready to finish up the Dana fabrication and found the front spring mounts in my Duster are 3/8" off center towards the driver's side. I could see it with the original 8-3/4 and figured it was just the perches. This summer I found the passenger front spring mount was off front to back by 1/4" so the rear was tracking to the left. I've fixed both but man, that seems like a lot! There doesn't appear to be any damage to the spring boxes.

Is this typical for them to come like this from the factory?

I would say yes, mine was similar. I centered mine off of the frame rails which may or may not be correct.

I had a '75 Duster that was like that.

almost every vehicle back in the day was built like that. i have never seen one that was to the factory blueprint.
it could be to either side, or front to back, and more often than not, both.

QC in the day was "yep, it rolls".. I've come to accept that you often have to make something crooked to make it look straight.

I would establish a centerline off of the rocker pinchwelds. And I would drop stringlines to check spring mounts front and rear, frame rails, etc. If one of the front perch mounts was closer to the center, you could put the spring perches on the housing offset, but I would probably fix or modify one or both of the mounts to get it right. 1/8" is not bad. 3/8" is a bunch.

Yep. Invest in a plumb bob.

Ha! I must have a Friday afternoon car...

It is good to know I'm not alone. The spring boxes are now fixed and everyrhing lines up. I thought long and hard about cheating the perches over but couldn't bring myself to do it.

Thanks everone!

Not unusual to be 1/4" off side/side, or in wheel opening locations.
I know of a couple Dusters that have a bow in one rocker at the door gap; neither car was ever hit or run aground or jacked up there. One bowed up, one down, one is right side, one is left.
Both cars track & drive straight.

Good. I'd rather see stuff fixed than half a$$ed. Put a few of these in the air and start dropping stringlines and you get to a point where if you find one that's reasonably straight, you're pleasantly surprised. Not just Mopars, but all of them from the muscle car era.

It would be interesting to know which/if any plants were better/worse than others, but 45-50 years on, facts would get muddied by restorations, wrecks, and repairs.