Was it just a preference of the line worker, regarding the orientation of the nut & bolt? ~ i.e. nut on the inside vs outside of the frame rail.
Seem like most of the pics show the nuts on the outside of the frame rail, but a few have them on the inside.
The reason I mentioned that is so that members and Marcus could keep an eye open for that detail to see if its plant specific. Sometimes its a results of how the line at that particular plant was set up - what station they were installed at or instructions received by that plant's managers. The one I posted that was different was a Dearborn example while the others were San Jose in that set - like the 70 Dearborn example you posted.
Looks like the 65-67 San Jose was typically done with bolts in plate with a few odd balls here and there - possible a single worker at that station that liked them the other way.
May be nothing or may turn out to be one of those details we discover like the direction of the front spring/shock cover bolts on the earlier cars which is somewhat plant specific
We'll only know if there is a pattern if we pay attention