I've finally gotten around to taking my rear leaf springs apart and I soaked them in some Evaporust overnight...
The part number is C7ZA5556AC, and just below that number on the driver's side it says 231E6 (8/19/1966), while the passenger side says 202E6 (7/21/1966). The paint markings for this particular leaf spring set-up appear to be green and white "splotches" on the shortest (bottom) leaf.
[2018 update: I now believe the paint markings were really green and silver...]
For reference, my car is a '67 390 GTA convertible built on Sept. 22, 1966 at the San Jose plant. Major options are the C6 automatic transmission, power steering, and power brakes (and it originally had the thermactor system as well).
Hope this adds another useful bit of information to the paint marking database...
