Fan to rad clearance (again)

[Ghoste]

I know this question has come up here a hundred times but I could only find one instance where someone asked about the distance between the rad and the hub of one of the viscous fan drives.  That particular one I could find was never really answered, so...
How far should the front of the thermostatic control on a viscous fan drive be from the radiator core?  I have a dimension for the fan blades so am I just overthinking this for now reason?  After all if the blades are at a specific dimension and the fan drives are all the same dimension in the viscous coupling portion NOT the hub going back to the water pump, then by default a correctly placed fan means a correctly placed hub, no?  Or are some of the viscous units different thicknesses?  The couple I have here all seem the same new or old.

[62 Max]

Depends on which viscous unit you have,thermostatic or torque drive.Thermostatic is 1 7/8" thick,torque drive is 1 1/4".Fan mounting surface to face of drive is the same.

[Ghoste]

It's a thermostatic one and the fan blades are exactly where I want them to be, it just seems to me like the face of the drive is too close.