Anyone know for sure if 66 L78 cars had power steering? Sometimes? Maybe?
Never?

Sometimes the L78 cars had power steering. Usually the people that went for the highest horsepower wanted every advantage in terms of free horsepower, so a power-robbing p/s setup was often omitted. The more radical the engine, the less compromise the driver would make to creature comforts (higher noise level, rough high idle, not as smooth running, higher fuel consumption etc. This is where the freaks played.)

Power steering was not known for having the greatest feedback, although the GM integral-type was a lot better than the typical linkage-boost type in that regard. Back in the days of old, people generally did not load their cars up with accessories like today, and they were a little more distrusting of complicated accessories. Besides, people often worked on their own cars and didn't like a lot of stuff getting in the way under the hood. Back in those days many people were used to manual steering. It is less likely that once you've gotten used to power steering that you'd be willing to go back to manual.

The L78 used larger diameter pullies on the alternator and the p/s pump so as to not overspeed those driven pumps while the engine wound into the high end of the RPM range (like upwards to 6000 rpm). On the short water pump models (pre '69) the manual steering solid lifter big block would use an idler pulley to help prevent belt slinging at high RPMs.

On the short water pump models (pre '69) the manual steering solid lifter big block would use an idler pulley to help prevent belt slinging at high RPMs.

The idler was ONLY used in 1966, and on ALL L78s, manual and power steering equipped... It was also used on 1966 L72 equipped fullsize cars...

There is a special cast iron deep groove PS pulley used for the L78. Not sure if the diameter is much bigger than stock (I sold it, so I can't check/compare), but the groove is deeper (single groove)... With the deep groove WP and crank pulleys, the "standard" PS pulley will NOT line up without shimming the brackets forward. Since the grooves are deeper and V-shaped, their groove centerlines are further apart...

Every original 1966 L78 I have seen (that I recall) had manual steering...

The idler was ONLY used in 1966, and on ALL L78s, manual and power steering equipped... It was also used on 1966 L72 equipped fullsize cars...

There is a special cast iron deep groove PS pulley used for the L78. Not sure if the diameter is much bigger than stock (I sold it, so I can't check/compare), but the groove is deeper (single groove)... With the deep groove WP and crank pulleys, the "standard" PS pulley will NOT line up without shimming the brackets forward. Since the grooves are deeper and V-shaped, their groove centerlines are further apart...

Every original 1966 L78 I have seen (that I recall) had manual steering...

Thanks for the clarification Tony!

Every original 1966 L78 I have seen (that I recall) had manual steering...

Ditto

Ditto X2.