The variation you mention is referred to as "setback" on the alignment sheet and is expressed in degrees. It's entirely possible that 1/2" would be in the correct range for the degrees number listed, usually something like .5 degrees (it's been a while since I thought about those things).
If the variation is a concern, one thing would be to make absolutely sure that the steering wheel is dead on center when the measuring is done. From there, you can triangulate the subframe and chassis dimensions (listed in the Chrysler service manual as to measuring points and lengths between measuring points) to make sure everything's "square" and in factory specs too. That can be somewhat time consuming, but might reveal a slight shift in some cases (deteriorated subframe rubber body mounts?). The body mounts are large rubber cushions that also have a center tube and rubber surrounding the tube where it indexes with the other half of the mount between the subframe and the body floorpan. Compared to GM's similar mounts, the Chrysler mounts were larger and of a harder compound, but they might still have some age issues. There also might be some gauge holes in the subframe that will align with similar holes in the body shell, to facilitate alignment
and also to use for "centering" functions too.
Doing the triangulation checks would require a drive-on lift (a twin-post lift might work also, but are a rare breed these days) so the suspension is at "ride height" and you can also have access from under the car. Otherwise, it's pretty easy to do but takes some time to do also.
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