Water Pump Center pilots, different sizes?

It seems the water pump hub on my 523 (stock pump), uses a larger pilot snout for a fan clutch, than any of the fan clutches I bought. Even the pump I have on the shelf from a 75 Torino with a 460 has a big snout, but the clutches all have a smaller pilot. I'm going to have it drilled larger.. But. What gives? Some quick Rockauto searches show the same pump used in every vehicle I checked.

429s/460s use the large hole, drilling it will work fine,or get the right clutch

All of the aftermarket clutches I have seen are already drilled for the big pilot, and the box contains a reducer bushing for those applications where the pump has a small pilot.

You might try a different parts store that has a different line of clutches and maybe those will be made like I described.

Greg

These were from two different stores. Figures. I drilled one out, we'll see how I did when I get the fan clutch spinning on the pulley.