yes thats what i meant the constant is the gasket surface LOL not the hub! So when the pump is built the outside of the hub will be pressed into the impellor until its = 4 15/32" from the gasket surface, not the other way around.
The shaft doesnt matter at all just as longs as its completly engaged with the impellor and hub. That way they ensure the fan mounting point is always the same. its B!
I just saw you live in new england i go to ames every friday, well keene anyway. its B! lol