How many have their parking brake cable above the spring? It seems to fit better that way but after detailed reading of section 4-3 of the 1968 service manual, I spotted a couple things.
3. Note: When installing spring, make sure spring is positioned so that parking brake cable is on underside of spring.
Also
9. If new mounting plate was installed, transfer parking brake cable retainer bracket to new plate.
I thought the parking cable fit better above the spring and 68 did not have parking brake cable retainer bracket.
I would think the service manual would be correct but I have seen errors.
If you notice 5-10 has the cushion protector on the cable and 5-10 view e looks like it would not. Mine has the cushion protector so I'll leave on top.
Mine are above the springs and even though the springs were replaced by a spring shop 25-30 years ago, I'm positive the cables always have been in the same place. I can see no way the cable (original) is long enough to be routed under the spring and then back up to the brake. Even if it made it, one bounce or lift of the car would tear it from either the frame or brake.
They go over the springs. This way if you ever Bo and Luke Duke your car over the river the brake cable won't be damaged. Also, if it is put on a lift and the wheels extend on the springs (fully) such as without the shock on it, they won't get pulled on or stretched.