Fan clutch or direct?

[khodne]

When was a direct fan used and when was a fan clutch used in 1970's?  Two 440 4-speed and one 440 auto are direct and a '70 383 4 speed has a clutch.  I am trying to figure out the why and when of usage.  Thank you.

[69_XS29L]

I thought manual 440s and A body 340s w/ low gears ( Track and Super Track Packs ) had the wider fan blades and fluid ( torque drive ) fan clutch. A/C cars had two different thermocoil clutches depending on gear ratio and engine size to lock the coupling at high temps. As built only, anything could have been changed in the last 40 yrs.
Good luck, Chango