cooperplace,
I confess I don't know much more about that era in South America than is covered in EKG's most excellent book that you'd mentioned above.
Pan American's history seems to avoid the political side of things as well.
However... I would suggest that the Aviation History & Nostalgia sub-forum might be able to steer you in the right direction.
There are some pretty cluey PPRuNers that read and contribute there.