I'm having trouble visualizing the strucural system with the brick haunch
that you are describing, but have some comments.
Brick constrction in Los Angeles in the 60's would have been reinforced,
probably about 10" thick made up of two wythes of 4" brick separated by a 2"
grout space in which steel reinforcing was embedded. I would be suprprised
to find 4" thich brick construction form that era.