fan clutch

[fireguyfire]

I realized today upon starting up my rebuild motor that the fan clutch on my 68 383 A/C car is completely gone!
Would my car have had the coil spring type, or the fluid filled type of clutch?
What is the difference between the 2 and what would happen if you put on the wrong kind?

[A383Wing]

I'm running the fluid kind without the spring in my cars....it moves the fan faster at idle and basically disengages at higher speed when the air moving through the radiator is sufficient enough to keep it cool. Never had any cooling issues at idle with this fan clutch. With the spring kind, it's basically free-wheeling all the time until the air going through the radiator fins gets hot enough to engage the clutch