Slide the clutch onto the delrin bushings, it may be a tight fit, that's OK.
Seat the clutch all the way down to the "hat" on the bushings. This automatically sets the gap between the fan hub and clutch.
What we don't want to see is this misalignment. Move your engine and triple bearing block to correct this.
Also look for sideways misalignment from the front or rear of the model. This may be caused by the engine being cocked sideways in the frames.