Actually the ECU just retards timing 6 degrees across all load points, it does not revert back to 10deg base timing.
The VS V8 has only one spark map, there are no high or low octane maps until later models.
The knock sensor is only used for some safety margin it does not mean the ECU activley advances spark until knock then backs it off some. It may do something similar if really crap fuel is used only due to the algorithm but it is not as smart as the late model vehicles which still really dont do it exactly like that. Really all that happens is you run off the main spark map, if some knock happens the timing is retarded (more for more knock, less for less knock) it then adds some spark back in after about 200mS, waits 200ms and adds some more back and keeps going until spark retard is 0 deg and you are back to the values in the main spark map.
VL Turbos had a knock sensor, no other VLs do from factory.