Chick,
The nut mounting direction in the AIM is for the reason you stated. Maybe this was a line workers error or possibly GM did things slightly different in LOS. I decided to assemble it the same (wrong) way when the car gets restored. I'll have photos to show it before the restoration. When at all possible I want to keep the few flaws (re: small paint runs in the door jamb by the pinchweld & firewall cowl top area) and any others I come across during the pre-restoration documenting.
I stumbled across the shackle mounting differences when I was installing new leaf springs in the convertible, and using the LOS car as a reference, had a heck of a time trying to get the upper bolt w/sleeve into the frame opening due to the fuel tank interference. That's when I looked in the AIM and discovered the difference. I reversed the direction and the install went quickly.
Mike