I use these on my tractors.
http://www.radiatorgenie.com/Radiator_Genie_p/rg1001.htm
They might work on the IDI.
I agree with garbage-Mechanic. I think the cooling issues are not so much the fan clutch but rather a restricted radiator internally or externally.
A plugged radiator or A/C coil can certainly cause cooling problems. But do not overlook the fact that the clutches on these trucks are a well known problem. Ford designed them to come on at the last minute, and the aftermarket ones can be junk, like most aftermarket stuff you buy now.